Fixed an issue where STOP SLAVE generated a warning to error log which test case couldn't handle, fixed by checking for io slave killed before checking for network error

WL#3951 - MyISAM: Additional Error Logs for Data Corruption
Fixed partition_repair_myisam.test.

Bug#35591 FLUSH PRIVILEGES caused a crash

A race condition on the privilege hash tables (proc_priv_hash
and func_priv_hash) caused one thread to try to delete elements
that had already been deleted by another thread.

The bug was caused by reading and saving the pointers to 
the hash tables outside mutex protection.  This led to an
inconsistency where a thread copied a pointer to a hash,
another thread did the same, the first thread then deleted
the hash, and the second then crashed when it in turn tried to
delete the deleted hash.

The fix is to ensure that operations on the shared hash structures
happens under mutex protection (moving the locking up a little)

Implemented a new INFORMATION_SCHEMA table, which is intended to
provide information about tablespaces.

The problem is not actually related to 2byte collation IDs.
The same crash happens if you change the collation ID in
mysql-test/str_data/Index.xml to a value smaller than 256.

Crash happened in SQL parser, because the "ident_map" and "state_map"
arrays were not initialized in loadable utf8 collations.

Fix: adding proper initialization of the "ident_map" and "state_map"
members for loadable utf8 collations.

Part II, engines instrumentation

Added back n_frees, use 'clear' instead of 'free' since memory is
not freed here.

Before this patch, semisync assumed transactions running in parallel
can not be larger than max_connections, but this is not true when
the event scheduler is executing events, and cause semisync run out
of preallocated transaction nodes.

Fix the problem by allocating transaction nodes dynamically.

This patch also fixed a possible deadlock when running UNINSTALL
PLUGIN rpl_semi_sync_master and updating in parallel. Fixed by
releasing the internal Delegate lock before unlock the plugins.

Add $basedir/lib/plugin to the search paths for semisync plugins.

    
When a .CSV file for table in the CSV engine contains
\X characters as part of unquoted fields, e.g.
    
2,naraya\nan
    
\n is not interpreted as a new line (it is however interpreted as a
newline in a quoted field).
    
The old algorithm copied the entire value for a unquoted field without
parsing the \X characters. 
    
The new algorithm adds the capability to handle \X characters in the 
unquoted fields of a .CSV file.