Fix assorted warnings that are generated in optimized builds.
Most of it is silencing variables that are set but unused.

This patch also introduces the MY_ASSERT_UNREACHABLE macro
which helps the compiler to deduce that a certain piece of
code is unreachable.

Fix assorted compiler warnings.

Tag or remove unused arguments and variables.

Ensure that fdatasync is properly declared as on Mac OS X, the
function is available but there is no prototype. Also, port a
fix for a warning from the InnoDB plugin over to the builtin. 

Tag unused arguments.
      
Approved by: Marko (via IRC)

Tag unused arguments.

Approved by: Marko (via IRC)

Fix assorted compiler warnings on Mac OS X.

           data dictionary confusion

On file systems with case insensitive file names, and
lower_case_table_names set to '2', the server could crash
due to a table definition cache inconsistency.  This is 
the default setting on MacOSX, but may also be set and
used on MS Windows.

The bug is caused by using two different strategies for
creating the hash key for the table definition cache, resulting
in failure to look up an entry which is present in the cache,
or failure to delete an existing entry.  One strategy was to
use the real table name (with case preserved), and the other
to use a normalized table name (i.e a lower case version).

This is manifested in two cases.  One is  during 'DROP DATABASE', 
where all known files are removed.  The removal from
the table definition cache is done via a generated list of
TABLE_LIST with keys (wrongly) created using the case preserved 
name.  The other is during CREATE TABLE, where the cache lookup
is also (wrongly) based on the case preserved name.
   
The fix was to use only the normalized table name when
creating hash keys.

           (variables_debug fails)

The problem was that "SET GLOBAL debug" could cause a crash on Solaris.
The crash happened if the server failed to open the trace file given in 
the "SET GLOBAL debug" statement. This caused an error message to be
printed to stderr containing the process name. However, printing to
stderr crashed the server since the pointer to the process name had
not been initialized.

This patch fixes the problem by initializing the process name 
properly when doing "SET GLOBAL debug".

No test case added as this bug was repeatable with existing test
coverage in variables_debug.test.

Enable the MySQL maintainer-specific development environment
(which add various warning related options to the compiler
flags) if debugging support is enabled.

because currently hostname stored in db in lowercase.

For crash testing: kill the server without generating core file.

include/my_dbug.h
  Use kill(getpid(), SIGKILL) which cannot be caught by signal handlers.
  All DBUG_XXX macros should be no-ops in optimized mode, do that for DBUG_ABORT as well.
sql/handler.cc
  Kill server without generating core.
sql/log.cc
  Kill server without generating core.

          replication aborts

When recieving a 'SLAVE STOP' command, slave SQL thread will roll back the
transaction and stop immidiately if there is only transactional table updated,
even through 'CREATE|DROP TEMPOARY TABLE' statement are in it. But These
statements can never be rolled back. Because the temporary tables to the user
session mapping remain until 'RESET SLAVE', Therefore it will abort SQL thread
with an error that the table already exists or doesn't exist, when it restarts
and executes the whole transaction again.

After this patch, SQL thread always waits till the transaction ends and then stops,
if 'CREATE|DROP TEMPOARY TABLE' statement are in it.

latest mysql-5.1-bugteam.

latest mysql-5.1-bugteam.

After ALTER TABLE which changed only table's metadata, row-based
binlog sometimes got corrupted since the tablemap was unexpectedly
set to 0 for subsequent updates to the same table.

ALTER TABLE which changed only table's metadata always reset
table_map_id for the table share to 0. Despite the fact that
0 is a valid value for table_map_id, this step caused problems
as it could have created situation in which we had more than
one table share with table_map_id equal 0. If more than one
table with table_map_id are 0 were updated in the same statement,
updates to these different tables were written into the same
rows event. This caused slave server to crash.

This bug happens only on 5.1. It doesn't affect 5.5+.

This patch solves this problem by ensuring that ALTER TABLE
statements which change metadata only never reset table_map_id
to 0. To do this it changes reopen_table() to correctly use
refreshed table_map_id value instead of using the old one/
resetting it.

When slave executes a transaction bigger than slave's max_binlog_cache_size,
slave will crash. It is caused by the assert that server should only roll back
the statement but not the whole transaction if the error ER_TRANS_CACHE_FULL 
happens. But slave sql thread always rollbacks the whole transaction when
an error happens.
            
Ather this patch, we always clear any error set in sql thread(it is different
from the error in 'SHOW SLAVE STATUS') and it is cleared before rolling back
the transaction.

This is a regression from the fix for bug no 38999. A storage engine capable
of reading only a subset of a table's columns updates corresponding bits in
the read buffer to signal that it has read NULL values for the corresponding
columns. It cannot, and should not, update any other bits. Bug no 38999
occurred because the implementation of UPDATE statements compare the NULL bits
using memcmp, inadvertently comparing bits that were never requested from the
storage engine. The regression was caused by the storage engine trying to
alleviate the situation by writing to all NULL bits, even those that it had no
knowledge of. This has devastating effects for the index merge algorithm,
which relies on all NULL bits, except those explicitly requested, being left
unchanged.

The fix reverts the fix for bug no 38999 in both InnoDB and InnoDB plugin and
changes the server's method of comparing records. For engines that always read
entire rows, we proceed as usual. For engines capable of reading only select
columns, the record buffers are now compared on a column by column basis. An
assertion was also added so that non comparable buffers are never read. Some
relevant copy-pasted code was also consolidated in a new function.

      
Suprisingly, a Slave_log_event would show up in the binary
log. This event is never used and should not appear in the
logs. As such, when the slave (or the mysqlbinlog tool) reads the
event, it will hit an invalid pointer (reference to the
descriptor event when deserializing the Slave_log_event was
purposodely set to NULL).
      
The presence of the Slave_log_event denotes a corrupted log, but
we cannot tell how the log got corrupted in the first
place. However, we can make the server cope with such events when
it reads them - in case of log corruption - and fail gracefully.
     
This patch makes the server/mysqlbinlog to report that it has
found an invalid log event when Slave_log_event is read.

Backported the patch for BUG#55452.

row_search_for_mysql(): Acquire an intention lock on the table
before locking the first record gap.

row_search_for_mysql(): Acquire an intention lock on the table
before locking the first record gap.