removing IMPOSSIBLE_RESULT from Item_result, as it's not
needed any more. The fact that an Item is not in a comparison
context is now always designated by IDENTITY_SUBST in Subst_constraint.
Previously IMPOSSIBLE_RESULT and IDENTITY_SUBST co-existed but
actually meant the same thing.

MDEV-8747 Wrong result for SELECT..WHERE derived_table_column='a' AND derived_table_column<>_latin1'A' COLLATE latin1_bin
MDEV-8749 Wrong result for SELECT..WHERE derived_table_enum_column='number' AND derived_table_enum_column OP number

MDEV-8753: 10.1 build is broken: xtradb/handler/ha_innodb.cc:21430: error: redefinition of 'void ib_push_warning(trx_t*, ulint, const char*, ...)'

Fixed bad merge.

Analysis: Server tried to continue reading tablespace using a cursor after
we had resolved that pages in the tablespace can't be decrypted.

Fixed by addind check is tablespace still encrypted.

   MDEV-8588: Assertion failure in file ha_innodb.cc line 21140 if at least one encrypted table exists and encryption service is not available

    Analysis: Problem was that in fil_read_first_page we do find that
    table has encryption information and that encryption service
    or used key_id is not available. But, then we just printed
    fatal error message that causes above assertion.

    Fix: When we open single table tablespace if it has encryption
    information (crypt_data) store this crypt data to the table
    structure. When we open a table and we find out that tablespace
    is not available, check has table a encryption information
    and from there is encryption service or used key_id is not available.
    If it is, add additional warning for SQL-layer.

MDEV-8588: Assertion failure in file ha_innodb.cc line 21140 if at least one encrypted table exists and encryption service is not available

Analysis: Problem was that in fil_read_first_page we do find that
table has encryption information and that encryption service
or used key_id is not available. But, then we just printed
fatal error message that causes above assertion.

Fix: When we open single table tablespace if it has encryption
information (crypt_data) store this crypt data to the table
structure. When we open a table and we find out that tablespace
is not available, check has table a encryption information
and from there is encryption service or used key_id is not available.
If it is, add additional warning for SQL-layer.

cosmetic fixes. test fixes.

MDEV-6066: Merge new defaults from 5.6 and 5.7 (defaults changed, QC can be stopped with no-zero size)

--autoset- command line prefix added

* Start_encryption_log_event
* --encrypt-binlog command line option

based on google patches.

Introduce Log_event_writer() that encapsulates
writing data to an IO_CACHE with automatic checksum calculation.

Now all events properly checksum themselves as needed.

Use Log_event_writer in MYSQL_BIN_LOG::write_cache() instead
of copy-pasting its logic all over.

Later Log_event_writer will also do encryption.

now when my_vsnprintf() supports %llu for a few years already.

commit f1abd015
Author: Andrei Elkin <aelkin@mysql.com>
Date:   Thu Nov 12 17:10:19 2009 +0200

    Bug #47210   first execution of "start slave until" stops too early

introduce DBUG_DUMP_EVENT_BUF,
remove few unused DBUG_EXECUTE_IF's
simplify few DBUG_PRINT's
remove few redundant #ifndef DBUG_OFF's

* replace binlog positions where they are calculated
  (instead of --disable_query_log)
* don't replace binlog positions when they're hard-coded anyway

1. use include/show_binlog_events.inc instead of SHOW BINLOG EVENTS
2. use include/show_relaylog_eventc.inc too
3. in all other places where a number might appear in the result
   file, include binlog_start_pos.inc, calculate the position
   like pos=`select $binlog_start_pos + 100`; and use
   replace_result $pos <pos>

and fix SHOW RELAYLOG 'src_name' EVENTS to respect src_name

* fix unireg.h includes
* use enum_binlog_checksum_alg for binlog checksum variables,
  not uint8

* reformat long lines
* remove useless 'const'
* remove unneeded do { ... } while(false} wrapper
* remove unneeded method

There are three Log_event::read_log_event() methods:
1. read the event image from IO_CACHE into String
2. create Log_event from the in-memory event image
3. read the event image from IO_CACHE and create Log_event

The 3rd was reading event image into memory and invoking the 2nd to
create Log_event. Now the 3rd also uses the 1st to read the event image
from IO_CACHE into memory, instead of duplicating its functionality.

remove my_crc_dbug_check (gdb can do it itself).
use 0 instead of my_checkum(0, 0, 0) - just as 10.0 does now.

Instead of encrypt(src, dst, key, iv) that encrypts all
data in one go, now we have encrypt_init(key,iv),
encrypt_update(src,dst), and encrypt_finish(dst).

This also causes collateral changes in the internal my_crypt.cc
encryption functions and in the encryption service.

There are wrappers to provide the old all-at-once encryption
functionality. But binlog events are often written piecewise,
they'll need the new api.

Rename reassociate to reset and create an inverse method release.
Method names are chosen to match std::unique_ptr methods.

make repeated cmake runs less verbose:
* remove few not very useful MESSAGE's
* only run pkg_check_modules() if there's no cached result
* only print QQGraph messages on the first run

Fix all cmake tests (including plugin) to use
MY_CHECK_AND_SET_COMPILER_FLAG. And fix that function
to be compatible with cmake 3.0. This way flag checks
are correctly cached (even in cmake 3.0) and properly reused.