Use sql_field->change parameter as the name of the field.

MDEV-5153: Server crashes in Item_ref::fix_fields on 2nd execution of PS with LEFT JOIN and MERGE view or SELECT SQ

1. Transformation of row IN subquery made the same as single value.
2. replace_where_subcondition() made working on several layers of OR/AND because it called on expression before fix_fields().

Singular Item_equal support added.

The problem was that during constant table substitution Item_equal become containing only one constant which was not supported internally.

MDEV-4435 Server crashes in my_strcasecmp_utf8 on ADD KEY IF NOT EXISTS with implicit name when the key exists.
        Use field name as a key name if the key name wasn't specified.

A clean-up: removing the code catching collation incompatibilities
from handler::check_collation_compatibility(), as the collation IDs
are already replaced at this point by TABLE_SHARE::init_from_binary_frm_image.

Modified according to the review comment

restore sergii@pisem.net-20120327141644-xue6r05x1giswwsm
that was lost in a merge

MDEV-4880 Attempt to create a table without columns produces ER_ILLEGAL_HA instead of ER_TABLE_MUST_HAVE_COLUMNS

+1 typo fixed

keywords that a statement could start from can only be
in the 'keyword' list, never in the 'keyword_sp'

allow ENGINE=FOOBAR in the discovering create table statement,
as long as the discovering engine is FOOBAR too

- Character set code & tests from Alexander Barkov
- Integration with ALTER TABLE, REPAIR and open_table from Monty

The problem was that MySQL 5.6 added some croatian and vitanamese character set collations that are incompatible with MariaDB.

The fix is to move the MariaDB conflicting collation numbers out of the region that MySQL is likely to use.
mysql_upgrade, REPAIR TABLE or ALTER TABLE will fix the collations.
If one tries to access and old incompatible table, one will get the error "Table upgrade required...."
After this patch, MariaDB supports all the MySQL character set collations and the old MariaDB croatian collations, which are closer to the latest standard than the MySQL versions.

New character sets:
ucs2_croatian_mysql561_uca_ci
utf8_croatian_mysql561_uca_ci
utf16_croatian_mysql561_uca_ci
utf32_croatian_mysql561_uca_ci
utf8mb4_croatian_mysql561_uca_ci

Other things:
- Fixed some compiler warnings
- mysql_upgrade prints information about repaired tables.
- Increased version number

VERSION:
  Increased VERSION number
client/mysqlcheck.c:
  Print repaired table name when using --verbose
include/m_ctype.h:
  Add new MariaDB collation regions that are not likely to conflict with MySQL
include/my_base.h:
  Added flag to detect if table was opened for ALTER TABLE
mysql-test/r/ctype_ldml.result:
  Updated result
mysql-test/r/ctype_uca.result:
  Updated result
mysql-test/r/ctype_upgrade.result:
  Updated result
mysql-test/r/ctype_utf16_uca.result:
  Updated result
mysql-test/r/ctype_utf32_uca.result:
  Updated result
mysql-test/r/ctype_utf8mb4_uca.result:
  Updated result
mysql-test/std_data/ctype_upgrade:
  Test files for testing upgrading of conflicting collations
mysql-test/suite/engines/funcs/r/db_alter_collate_ascii.result:
  New collations added
mysql-test/suite/engines/funcs/r/db_alter_collate_utf8.result:
  New collations added
mysql-test/suite/innodb/r/innodb_ctype_ldml.result:
  Updated test result
mysql-test/suite/innodb/t/innodb_ctype_ldml.test:
  Updated test result
mysql-test/suite/plugins/r/show_all_plugins.result:
  Updated version number
mysql-test/suite/roles/create_and_drop_role_invalid_user_table.result:
  Updated version number
mysql-test/t/ctype_ldml.test:
  Updated test
mysql-test/t/ctype_uca.test:
  Testing of new collations
mysql-test/t/ctype_upgrade.test:
  Testing of upgrading tables with old collations
  The test ensures that:
  - We will get an error if we try to open a table with old collations.
  - CHECK TABLE will detect that the table needs to be upgraded.
  - ALTER TABLE and REPAIR will fix the table.
  - mysql_upgrade works as expected
mysql-test/t/ctype_utf16_uca.test:
  Testing of new collations
mysql-test/t/ctype_utf32_uca.test:
  Testing of new collations
mysql-test/t/ctype_utf8mb4_uca.test:
  Testing of new collations
mysys/charset-def.c:
  Added new character sets
mysys/charset.c:
  Always give an error, if requested, if a character set didn't exist
sql/handler.cc:
  - Added upgrade_collation() to check if collation is compatible with old version
  - check_collation_compatibility() checks if we are using an old collation from MariaDB 5.5 or MySQL 5.6
  - ha_check_for_upgrade() returns HA_ADMIN_NEEDS_ALTER if we have an incompatible collation
sql/handler.h:
  Added new prototypes
sql/sql_table.cc:
  - Mark that tables are opened for ALTER TABLE
  - If table needs to be upgraded, ensure we are not using online alter table.
sql/table.cc:
  - If we are using an old incompatible collation, change to use the new one and mark table as incompatible.
  - Give an error if we try to open an incompatible table.
sql/table.h:
  Added error that table needs to be rebuild
storage/connect/ha_connect.cc:
  Fixed compiler warning
strings/ctype-uca.c:
  New character sets

The loop in the binary search in remove_status_vars() was
incorrectly implemented and could continue infinitely in some cases.
Rewrote the binary search code.

Delete any left-over deferred_event from rpl_group_info when
deleting the parent object, to protect against memory leaks.

Remove rpl_group_info from THD before freeing it,
to avoid access-after-free in THD.

Tested manually that crash in the middle of writing transaction on the master
does correctly cause a rollback on slave, so remove the corresponding ToDo.