MDEV-7563 Support CHECK constraint as in (or close to) SQL Standard

MDEV-10134 Add full support for DEFAULT

- Added support for using tables with MySQL 5.7 virtual fields,
  including MySQL 5.7 syntax
- Better error messages also for old cases
- CREATE ... SELECT now also updates timestamp columns
- Blob can now have default values
- Added new system variable "check_constraint_checks", to turn of
  CHECK constraint checking if needed.
- Removed some engine independent tests in suite vcol to only test myisam
- Moved some tests from 'include' to 't'. Should some day be done for all tests.
- FRM version increased to 11 if one uses virtual fields or constraints
- Changed to use a bitmap to check if a field has got a value, instead of
  setting HAS_EXPLICIT_VALUE bit in field flags
- Expressions can now be up to 65K in total
- Ensure we are not refering to uninitialized fields when handling virtual fields or defaults
- Changed check_vcol_func_processor() to return a bitmap of used types
- Had to change some functions that calculated cached value in fix_fields to do
  this in val() or getdate() instead.
- store_now_in_TIME() now takes a THD argument
- fill_record() now updates default values
- Add a lookahead for NOT NULL, to be able to handle DEFAULT 1+1 NOT NULL
- Automatically generate a name for constraints that doesn't have a name
- Added support for ALTER TABLE DROP CONSTRAINT
- Ensure that partition functions register virtual fields used. This fixes
  some bugs when using virtual fields in a partitioning function

sql/sql_priv.h

@@ -126,7 +126,7 @@
 #define TMP_TABLE_ALL_COLUMNS   (1ULL << 12)    // SELECT, intern
 #define OPTION_WARNINGS         (1ULL << 13)    // THD, user
 #define OPTION_AUTO_IS_NULL     (1ULL << 14)    // THD, user, binlog
-#define OPTION_FOUND_COMMENT    (1ULL << 15)    // SELECT, intern, parser
+#define OPTION_NO_CHECK_CONSTRAINT_CHECKS  (1ULL << 14)
 #define OPTION_SAFE_UPDATES     (1ULL << 16)    // THD, user
 #define OPTION_BUFFER_RESULT    (1ULL << 17)    // SELECT, user
 #define OPTION_BIN_LOG          (1ULL << 18)    // THD, user
@@ -183,6 +183,7 @@
 #define OPTION_ALLOW_BATCH              (1ULL << 36) // THD, intern (slave)
 #define OPTION_SKIP_REPLICATION         (1ULL << 37) // THD, user
 #define OPTION_RPL_SKIP_PARALLEL        (1ULL << 38)
+#define OPTION_FOUND_COMMENT            (1ULL << 39) // SELECT, intern, parser
 
 /* The rest of the file is included in the server only */
 #ifndef MYSQL_CLIENT