Patially merge WL#5917, to understand v2 row events

fix a copy-paste error, introduced in role refactoring

fix the code to compile with clang. fix warnings too.

include/probes_mysql_nodtrace.h:
  clang++ doesn't like numeric _constants_ being used in ||
  (it suspects that the intention was | ). Boolean constants are ok.
sql/hostname.cc:
  only used in DBUG_ASSERT
sql/item.cc:
  str_to_time and str_to_datetime return bool, not MYSQL_TIMESTAMP_xxx
sql/item_func.cc:
  str_to_datetime_with_warn() returns bool, not MYSQL_TIMESTAMP_xxx
storage/cassandra/CMakeLists.txt:
  CMAKE_CXX_FLAGS can be empty
storage/connect/odbconn.cpp:
  HWND is void*
storage/connect/user_connect.h:
  deprecated on FreeBSD and unused anyway
storage/connect/value.cpp:
  bad characters inside. unused.
storage/spider/spd_trx.cc:
  clang++ warns that memset will also overwrite vtbl. it might be as well a good idea,
  as it asserts that the object will only be used as a storage.
  silence the warning.

when frm file exists, but the table does not.

In recover_from_failed_open(), allow the discovery
to fail without an error, when
open_strategy == TABLE_LIST::OPEN_IF_EXISTS.

merged from 5.6:
Bug#14521864: MYSQL 5.1 TO 5.5 BUGS PARTITIONING
Bug#16589511: MYSQL_UPGRADE FAILS TO WRITE OUT ENTIRE ALTER TABLE ... ALGORITHM= ... STATEMENT
Bug#16274455: CAN NOT ACESS PARTITIONED TABLES WHEN DOWNGRADED FROM 5.6.11 TO 5.6.10

plus minor changes from 5.6, mainly comments

Fixing include/ctype_datetime.inc not to depend on the current time zone.

            into 10.0

            into 10.0

"mtr ctype_ldml" failed when compiled with "gcc -funsigned-char".
Changing the code not to depend on the signed/unsigned compiler defaults
for the "char" data type.

Fixed.

Fixed.

in the code merged from MySQL-5.6:

  const CHARSET_INFO* -> CHARSET_INFO*

(CHARSET_INFO already has the "const" qualifier in MariaDB, inlike in MySQL)

Applied a patch from Philip Hazel implementing the non-standard
syntax for word boundaries in PCRE, for compatibility with the
old Henry Spencer's regex library.

modified:
  storage/connect/valblk.cpp

modified:
  storage/connect/ha_connect.cc
  storage/connect/value.cpp

- Fix the way GetPlug works (was not updating xp)

modified:
  storage/connect/ha_connect.cc

modified:
  storage/connect/odbconn.cpp

- Prepare Value and Valblk to support unsigned data types
  (not operational yet)

modified:
  storage/connect/colblk.cpp
  storage/connect/filamvct.cpp
  storage/connect/myconn.cpp
  storage/connect/plgdbutl.cpp
  storage/connect/tabdos.cpp
  storage/connect/tabodbc.cpp
  storage/connect/tabvct.cpp
  storage/connect/valblk.cpp
  storage/connect/valblk.h
  storage/connect/value.cpp
  storage/connect/value.h
  storage/connect/xindex.cpp

            MariaDB 10.0 server

modified:
  storage/connect/ha_connect.cc
  storage/connect/myconn.cpp
  storage/connect/myutil.cpp
  storage/connect/odbccat.h
  storage/connect/odbconn.cpp
  storage/connect/tabmysql.cpp

- Add tests on new MYSQL features

added:
  storage/connect/mysql-test/connect/my.cnf
  storage/connect/mysql-test/connect/r/mysql_discovery.result
  storage/connect/mysql-test/connect/r/mysql_exec.result
  storage/connect/mysql-test/connect/r/mysql_new.result
  storage/connect/mysql-test/connect/t/myconn.inc
  storage/connect/mysql-test/connect/t/myconn_cleanup.inc
  storage/connect/mysql-test/connect/t/mysql_discovery.test
  storage/connect/mysql-test/connect/t/mysql_exec.test
  storage/connect/mysql-test/connect/t/mysql_new.test

Analysis: In earlier MySQL 5.6 versions this table innodb_index_stats  used to have a foreign key referencing to innodb_table_stats. However, in newer MySQL 5.6 versions this foreign key is removed and if you upgrade, your innodb_table_stats is created by the earlier mariadb version, thus a newer version will complain that the table is incorrectly defined.

Added drop foreign key on mysql_system_tables_fix.sql to be executed on mysql_upgrade.

Fixed the following compilation errors and test failures:
- maria SE: "stage_waiting_for_a_resource" wasn't declared w/o PFS
- sql_repl.h: PSI_mutex_key is not available in non-PFS builds
- mysqld.cc: pfs_param is not available in non-PFS builds
- mysqld.cc: init_show_explain_psi_keys() is not available in non-PFS builds
- mysqld.cc: call net_before_header_psi, net_after_header_psi even if PFS
  is not available so that thread enters stage_init at proper time. Fixes
  sp-threads and a few tests in funcs_1.
- myisam_file_io.opt: added missing loose prefix

        Added the IF NOT EXISTS option to the CONSTRAINT keyword.

MDEV-5248 Serious incompatibility and data corruption of DATETIME and DATE types due to get_innobase_type_from_mysql_type refactor combined with InnoDB Online DDL

restore old innodb get_innobase_type_from_mysql_type() function,
record all mysql_type->innodb_type mapping
(as generated by mysql-5.6).
add safety code to disable online alter when internal types don't match

storage/innobase/dict/dict0stats.cc:
  revert to 5.6 state

correct bugs in mysql_system_tables_fix.sql.
Update system_mysql_db_fix* tests