plugin_dir option backported from 5.1

            
            test_if_data_home_dir fixed to look into real path.
            Checks added to mi_open for symlinks into data home directory.

per-file messages:
        include/my_sys.h
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          my_is_symlink interface added
        include/myisam.h
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          myisam_test_invalid_symlink interface added
        myisam/mi_check.c
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          mi_open_datafile calls modified
        myisam/mi_open.c
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          code added to mi_open to check for symlinks into data home directory.
          mi_open_datafile now accepts 'original' file path to check if it's
          an allowed symlink.
        myisam/mi_static.c
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          myisam_test_invlaid_symlink defined
        myisam/myisamchk.c
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          mi_open_datafile call modified
        myisam/myisamdef.h
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          mi_open_datafile interface modified - 'real_path' parameter added
        mysql-test/r/symlink.test
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          error codes corrected as some patch now rejected pointing inside datahome
        mysql-test/r/symlink.result
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          error messages corrected in the result
        mysys/my_symlink.c
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          my_is_symlink() implementsd
          my_realpath() now returns the 'realpath' even if a file isn't a symlink
        sql/mysql_priv.h
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          test_if_data_home_dir interface
        sql/mysqld.cc
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          myisam_test_invalid_symlik set with the 'test_if_data_home_dir'
        sql/sql_parse.cc
          Bug#32167 another privilege bypass with DATA/INDEX DIRECTORY.
          
          error messages corrected
          test_if_data_home_dir code fixed

add'l portability fixes

portability fixes / cleanup

Bug#37531, Bug#36941, Bug#36941, Bug#36942, Bug#38185.

Also include test case from Bug 34300 which was left out from earlier snapshot
(5.1-ss2387).

Also include fix for Bug #29507, "TRUNCATE shows to many rows effected", since
the fix for Bug 37531 depends on it.

post push fix for bug#20129, test failed due to non existing
source files.

created at least some files and that they are correct.

Send_field.org_col_name has broken value on secondary execution.
It happens when result field is created from the field which belongs to view
due to forgotten assignment of some Send_field attributes. 
The fix:
set Send_field.org_col_name,org_table_name with correct value during Send_field intialization.

Bug #35602 "Failed to read auto-increment value from storage engine" with
Innodb

The test for REPLACE was an error of ommission since it's classified as
a simple INSERT. For REPLACE statements we don't acquire the special
AUTOINC lock for AUTOINC_NEW_STYLE_LOCKING with this fix.

Bug#36600 and Bug#36793:

Bug #36600 SHOW STATUS takes a lot of CPU in buf_get_latched_pages_number

Fix by removing the Innodb_buffer_pool_pages_latched variable from SHOW
STATUS output in non-UNIV_DEBUG compilation.

Bug #36793 rpl_innodb_bug28430 fails on Solaris

This is a back port from branches/zip. This code has been tested on a
big-endian machine too.

Bug #36278 Data_free in SHOW TABLE STATUS for InnoDB is in kilobytes

Change the fix for Bug 32440 to show bytes instead of kilobytes in
INFORMATION_SCHEMA.TABLES.DATA_FREE.

INSTALL PLUGIN and UNINSTALL PLUGIN worked with statement-based and
mixed-mode replication only, but not with row-based replication.

There is no statement-based replication of these statements.
But there was row-based replication of the inserts and deletes
to and from the mysql.plugin table.

The fix is to suppress binlogging during insert and delete to
and from the mysql.plugin table.

We could allocate chunks larger than 4GB, but did our
size-accounting in 32-bit values. This could lead to
spurious warnings, inaccurate accounting, and, in
theory, data loss.
  
Affected: 64-bit platforms. Debug-build (with safemalloc).
At least one buffer larger than 4GB. For potential data
loss, a re-alloc on such a buffer would be necessary.

  - Before sending EOF, check if we've already sent an error.

is used causes server crash.
  Revert the fix : unstable test case revealed by pushbuild

Bug#35161
Fixed memory leak when failing to open a partition.

Bug#20129
Added tests for verifying REPAIR PARTITION.

more clever gcc version checking.