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

mysql-test/r/gis.result

@@ -614,8 +614,6 @@ t1	CREATE TABLE `t1` (
 drop table t1;
 CREATE TABLE `t1` (`object_id` bigint(20) unsigned NOT NULL default '0', `geo`
 geometry NOT NULL default '') ENGINE=MyISAM ;
-Warnings:
-Warning	1101	BLOB/TEXT column 'geo' can't have a default value
 insert into t1 values ('85984',GeomFromText('MULTIPOLYGON(((-115.006363
 36.305435,-114.992394 36.305202,-114.991219 36.305975,-114.991163
 36.306845,-114.989432 36.309452,-114.978275 36.312642,-114.977363