This deadlock could occour betweeen one connection executing
SET GLOBAL EVENT_SCHEDULER= ON and another executing SET GLOBAL
EVENT_SCHEDULER= OFF. The bug was introduced by WL#4738.

The first connection would hold LOCK_event_metadata (protecting
the global variable) while trying to lock LOCK_global_system_variables
starting the event scheduler thread (in THD:init()).

The second connection would hold LOCK_global_system_variables
while trying to get LOCK_event_scheduler after stopping the event
scheduler inside event_scheduler_update().

This patch fixes the problem by not using LOCK_event_metadata to
protect the event_scheduler variable. It is still protected using
LOCK_global_system_variables. This fixes the deadlock as it removes 
one of the two mutexes used to produce it.

However, this patch opens up the possibility that the event_scheduler
variable and the real event_scheduler state can become out of sync
(e.g. variable = OFF, but scheduler running). But this can only
happen under very unlikely conditions - two concurrent SET GLOBAL
statments, with one thread interrupted at the exact wrong moment.
This is preferable to having the possibility of a deadlock.

This patch also fixes a bug where it was possible to exit create_event()
without releasing LOCK_event_metadata if running out of memory during
its exection.

No test case added since a repeatable test case would have required
excessive use of new sync points. Instead we rely on the fact that
this bug was easily reproduceable using RGQ tests.

There are two issues fixed here:

  1. We needed to update the result file, for some of 
     mysqlbinlog_* tests, because now the some padding chars
     are not output anymore.

  2. We needed to change the Field_string::pack so that
     for BINARY types the padding chars are not packed 
     (lengthsp will return full length for these types).

The problem is introduced by WL#4435 "Support OUT-parameters in 
prepared statements".
When a statement that has out parameters was reprepared,
the reprepare request error was ignored, and an
attempt to send out parameters to the client was made.

Since the out parameter list was not initialized in case
of an error, this attempt led to a crash.

Don't try to send out parameters to the client
if an error occurred in statement execution.

- Fixing crash on attempt to create a fulltext index with an utf8mb4 column
- fixing wrong border width  for supplementary characters in mysql client:

  mysql --default-character-set=utf8mb4 -e "select concat(_utf32 0x20000,'a')"

Split rpl_row_charset into:

  - rpl_row_utf16.
  - rpl_row_utf32.

This way these tests can run independently if server supports
either one of the charsets but not both.

Cleaned up rpl_row_utf32 which had a spurious instruction:
-- let $reset_slave_type_conversions= 0

In BUG#51787 we were using the wrong charset to print out the
data. We were using the field charset for the string that would
hold the information. This caused the assertion, because the
string length was not aligned with UTF32 bytes requirements for
storage.

We fix this by using &my_charset_latin1 in the string object
instead of the field->charset(). As a side-effect, we needed to
extend the show_sql_type interface so that it took the field
charset is now passed as a parameter, so that one is able to
calculate the correct field size.

In BUG#51716 we had issues with Field_string::pack and
Field_string::unpack. When packing, the length was incorrectly
calculated. When unpacking, the padding the string would be
padded with the wrong bytes (a few bytes less than it should).

We fix this by resorting to charset abstractions (functions) that
calculate the correct length when packing and pad correctly the
string when unpacking.

LOCK kills the server.

Prohibit FLUSH TABLES WITH READ LOCK application to views or
temporary tables.
Fix a subtle bug in the implementation when we actually
did not remove table share objects from the table cache after 
acquiring exclusive locks.

The problem was that in read only mode (read_only enabled),
the server would mistakenly deny data modification attempts
for temporary tables which belong to a transactional storage
engine (eg. InnoDB).

The solution is to allow transactional temporary tables to be
modified under read only mode. As a whole, the read only mode
does not apply to any kind of temporary table.

    Plugins included into bin release cannot be
    installed on debug version of server

Ensure that the plugin files of the debug build
get into the optimized tree, so that they find
their way into the final RPMs.

    Plugins included into bin release cannot be
    installed on debug version of server

IF    the build process was split into separate "debug" and
      "optimized" builds
   AND
      the plugin files of the debug build got copied into
      "plugin/debug/"
(both is done for MySQL release builds starting from 5.5.3),
THEN these debug plugin files are to be included in the
     final binary package.

This change deals with the inclusion only,
the other parts are done in different changesets.

This is a fix specific for HPUX,
for which the compiler does not resolve properly dependencies
involving unused inline functions.
(See existing comments in mysql_thread.h)

In include/mysql/psi/mysql_thread.h,
the instrumentation helpers for mysql_prlock_*
uses the pr lock apis.

These apis are implemented in mysys/thr_rwlock.c,
which is not linked to client code.

As a result, the code does not link in libmysql_r, on HPUX.

The fix is to cut dependencies explicitely,
by introducing -DDISABLE_MYSQL_RWLOCK_H,
when building client code.

Ensure that we store the correct cached_field_type whenever we cache Field items
(in this case it allows us to compare dates as dates, rather than strings)