As a side-effect of purge_relay_logs(), sql_slave_skip_counter
was silently ignored in GTID mode.

But sql_slave_skip_counter in fact is not a good match with GTID.
And it is not really needed either, as users can explicitly set
@@gtid_slave_pos to skip specific GTIDs, in a way that matches
well how GTID replication works.

So with this patch, we give an error on attempts to set
sql_slave_skip_counter when using GTID, with a suggestion to use
gtid_slave_pos instead, if needed.

    MDEV-4984: Implement MASTER_GTID_WAIT() and @@LAST_GTID.
    MDEV-4726: Race in mysql-test/suite/rpl/t/rpl_gtid_stop_start.test
    MDEV-5636: Deadlock in RESET MASTER

Fix a race in test case rpl_gtid_basic.
include/sync_with_master_gtid.inc got confused due to two different
GTIDs both with the same seq_no=9.

The problem is a deadlock between MYSQL_BIN_LOG::reset_logs() and
MYSQL_BIN_LOG::mark_xid_done(). The former takes LOCK_log and waits for the
latter to complete. But the latter also tries to take LOCK_log; this can lead
to a deadlock.

There was already code that tries to deal with this, with the flag
reset_master_pending. However, there was still a small opportunity for
deadlock, when an previous mark_xid_done() is still running when reset_logs()
is called and is at the precise point where it first releases LOCK_xid_list
and then re-aquires both LOCK_log and LOCK_xid_list.

Solve by setting reset_master_pending in reset_logs() before taking
LOCK_log. And also count how many invocations of LOCK_xid_list are in the
progress of releasing and re-aquiring locks, and in reset_logs() wait for that
number to drop to zero after setting reset_master_pending and before taking
LOCK_log.

Rewrite the gtid_waiting::wait_for_gtid() function.
The code was rubbish (and buggy). Now the logic is
much clearer.

Also fix a missing slave sync that could cause test failure.

Couple of small fixes following buildbot testing.

Some GTID test cases were using include/wait_condition.inc with a
condition like SELECT COUNT(*)=4 FROM t1 to wait for the slave to
catch up with the master. This causes races and test failures, as the
changes to the tables become visible at the COMMIT of the SQL thread
(or even before in case of MyISAM), but the changes to
@@gtid_slave_pos only become visible a little bit after the COMMIT.

Now that we have MASTER_GTID_WAIT(), just use that to sync up in a
GTID-friendly way, wrapped in nice include/save_master_gtid.inc and
include/sync_with_master_gtid.inc scripts.

MASTER_GTID_WAIT() is similar to MASTER_POS_WAIT(), but works with a
GTID position rather than an old-style filename/offset.

@@LAST_GTID gives the GTID assigned to the last transaction written
into the binlog.

Together, the two can be used by applications to obtain the GTID of
an update on the master, and then do a MASTER_GTID_WAIT() for that
position on any read slave where it is important to get results that
are caught up with the master at least to the point of the update.

The implementation of MASTER_GTID_WAIT() is implemented in a way
that tries to minimise the performance impact on the SQL threads,
even in the presense of many waiters on single GTID positions (as
from @@LAST_GTID).

(as it was done for spider suite)

MDEV-4439 ALTER TABLE .. [ADD|DROP] FOREIGN KEY IF [NOT] EXISTS does not work if constraint name is not used.
  Patches for server and the Innodb engine.
  Server is fixed so it does nothing if no indexes left to alter.
  Innodb parser is fixed so it looks for the IF [NOT] EXISTS option in a string.
  Another change is that it uses the index name for the internal dictionary.
  Prior to that it only used the CONSTRAINT name for it.

mysql-test/r/lowercase_table2.result:
  Updated result
  (The change happend because we don't try to open the table anymore as part of create table)
mysql-test/suite/rpl/r/create_or_replace_mix.result:
  Fixed result file
mysql-test/suite/rpl/r/create_or_replace_row.result:
  Fixed result file
mysql-test/suite/rpl/r/create_or_replace_statement.result:
  Fixed result file
mysql-test/suite/rpl/t/create_or_replace.inc:
  Drop open temporary table
mysys/my_delete.c:
  Added missing newline
plugin/metadata_lock_info/mysql-test/metadata_lock_info/r/user_lock.result:
  Fixed result
  (Lock names was before off by one. Was corrected by my previous patch)
sql/sql_select.cc:
  Fixed compiler warnings by adding missing casts
storage/connect/ha_connect.cc:
  Fixed compiler warnings
storage/innobase/os/os0file.cc:
  Fixed compiler warnings
storage/xtradb/btr/btr0btr.cc:
  Fixed compiler warnings
storage/xtradb/handler/ha_innodb.cc:
  removed not used function
strings/ctype-uca.c:
  Fixed compiler warnings
support-files/compiler_warnings.supp:
  Added suppression for warnings that are wrong or are not serious andthat we don't plan to fix.

mysql-test/r/create_or_replace.result:
  Added test case
mysql-test/t/create_or_replace.test:
  Added test case
sql/sql_base.cc:
  Downgrade locks in LOCK TABLES + CREATE TABLE OR REPLACE
sql/sql_table.cc:
  Downgrade locks in LOCK TABLES + CREATE TABLE OR REPLACE

it didn't help, instead it only broke upgrades even more

- CREATE TABLE is by default executed on the slave as CREATE OR REPLACE
- DROP TABLE is by default executed on the slave as DROP TABLE IF NOT EXISTS

This means that a slave will by default continue even if we try to create
a table that existed on the slave (the table will be deleted and re-created) or
if we try to drop a table that didn't exist on the slave.
This should be safe as instead of having the slave stop because of an inconsistency between
master and slave, it will fix the inconsistency.
Those that would prefer to get a stopped slave instead for the above cases can set slave_ddl_exec_mode to STRICT. 

- Ensure that a CREATE OR REPLACE TABLE which dropped a table is replicated
- DROP TABLE that generated an error on master is handled as an identical DROP TABLE on the slave (IF NOT EXISTS is not added in this case)
- Added slave_ddl_exec_mode variable to decide how DDL's are replicated

New logic for handling BEGIN GTID ... COMMIT from the binary log:

- When we find a BEGIN GTID, we start a transaction and set OPTION_GTID_BEGIN
- When we find COMMIT, we reset OPTION_GTID_BEGIN and execute the normal COMMIT code.
- While OPTION_GTID_BEGIN is set:
  - We don't generate implict commits before or after statements
  - All tables are regarded as transactional tables in the binary log (to ensure things are executed exactly as on the master)
- We reset OPTION_GTID_BEGIN also on rollback

This will help ensuring that we don't get any sporadic commits (and thus new GTID's) on the slave and will help keep the GTID's between master and slave in sync.


mysql-test/extra/rpl_tests/rpl_log.test:
  Added testing of mode slave_ddl_exec_mode=STRICT
mysql-test/r/mysqld--help.result:
  New help messages
mysql-test/suite/rpl/r/create_or_replace_mix.result:
  Testing of CREATE OR REPLACE TABLE with replication
mysql-test/suite/rpl/r/create_or_replace_row.result:
  Testing of CREATE OR REPLACE TABLE with replication
mysql-test/suite/rpl/r/create_or_replace_statement.result:
  Testing replication of create or replace
mysql-test/suite/rpl/r/rpl_gtid_startpos.result:
  Test must be run in slave_ddl_exec_mode=STRICT as part of the test depends on that DROP TABLE should fail on slave.
mysql-test/suite/rpl/r/rpl_row_log.result:
  Updated result
mysql-test/suite/rpl/r/rpl_row_log_innodb.result:
  Updated result
mysql-test/suite/rpl/r/rpl_row_show_relaylog_events.result:
  Updated result
mysql-test/suite/rpl/r/rpl_stm_log.result:
  Updated result
mysql-test/suite/rpl/r/rpl_stm_mix_show_relaylog_events.result:
  Updated result
mysql-test/suite/rpl/r/rpl_temp_table_mix_row.result:
  Updated result
mysql-test/suite/rpl/t/create_or_replace.inc:
  Testing of CREATE OR REPLACE TABLE with replication
mysql-test/suite/rpl/t/create_or_replace_mix.cnf:
  Testing of CREATE OR REPLACE TABLE with replication
mysql-test/suite/rpl/t/create_or_replace_mix.test:
  Testing of CREATE OR REPLACE TABLE with replication
mysql-test/suite/rpl/t/create_or_replace_row.cnf:
  Testing of CREATE OR REPLACE TABLE with replication
mysql-test/suite/rpl/t/create_or_replace_row.test:
  Testing of CREATE OR REPLACE TABLE with replication
mysql-test/suite/rpl/t/create_or_replace_statement.cnf:
  Testing of CREATE OR REPLACE TABLE with replication
mysql-test/suite/rpl/t/create_or_replace_statement.test:
  Testing of CREATE OR REPLACE TABLE with replication
mysql-test/suite/rpl/t/rpl_gtid_startpos.test:
  Test must be run in slave_ddl_exec_mode=STRICT as part of the test depends on that DROP TABLE should fail on slave.
mysql-test/suite/rpl/t/rpl_stm_log.test:
  Removed some lines
mysql-test/suite/sys_vars/r/slave_ddl_exec_mode_basic.result:
  Testing of slave_ddl_exec_mode
mysql-test/suite/sys_vars/t/slave_ddl_exec_mode_basic.test:
  Testing of slave_ddl_exec_mode
sql/handler.cc:
  Regard all tables as transactional in commit if OPTION_GTID_BEGIN is set.
  This is to ensure that statments are not commited too early if non transactional tables are used.
sql/log.cc:
  Regard all tables as transactional in commit if OPTION_GTID_BEGIN is set.
  Also treat 'direct' log events as transactional (to get them logged as they where on the master)
sql/log_event.cc:
  Ensure that the new error from DROP TABLE when trying to drop a view is treated same as the old one.
  Store error code that slave expects in THD.
  Set OPTION_GTID_BEGIN if we find a BEGIN.
  Reset OPTION_GTID_BEGIN if we find a COMMIT.
sql/mysqld.cc:
  Added slave_ddl_exec_mode_options
sql/mysqld.h:
  Added slave_ddl_exec_mode_options
sql/rpl_gtid.cc:
  Reset OPTION_GTID_BEGIN if we record a gtid (safety)
sql/sql_class.cc:
  Regard all tables as transactional in commit if OPTION_GTID_BEGIN is set.
sql/sql_class.h:
  Added to THD: log_current_statement and slave_expected_error
sql/sql_insert.cc:
  Ensure that CREATE OR REPLACE is logged if table was deleted.
  Don't do implicit commit for CREATE if we are under OPTION_GTID_BEGIN
sql/sql_parse.cc:
  Change CREATE TABLE -> CREATE OR REPLACE TABLE for slaves
  Change DROP TABLE -> DROP TABLE IF EXISTS for slaves
  CREATE TABLE doesn't force implicit commit in case of OPTION_GTID_BEGIN
  Don't do commits before or after any statement if OPTION_GTID_BEGIN was set.
sql/sql_priv.h:
  Added OPTION_GTID_BEGIN
sql/sql_show.cc:
  Enhanced store_create_info() to also be able to handle CREATE OR REPLACE
sql/sql_show.h:
  Updated prototype
sql/sql_table.cc:
  Ensure that CREATE OR REPLACE is logged if table was deleted.
sql/sys_vars.cc:
  Added slave_ddl_exec_mode
sql/transaction.cc:
  Added warning if we got a GTID under OPTION_GTID_BEGIN

Unlike MyISAM, InnoDB does not support boolean full-text searches on 
nonindexed columns, but this restriction was not enforced, resulting 
in queries that returned incorrect results. (Bug #16434374)

appears to be unset, or when it contains 'root' even though the user
does not have real root permissions

Turned off Performance Schema for Spider test suite

Rules performed unnecessary copying which made tests run with wrong
global testdir