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/subselect_no_exists_to_in.result

@@ -1936,7 +1936,7 @@ create table t1(id int);
 create table t2(id int);
 create table t3(flag int);
 select (select * from t3 where id not null) from t1, t2;
-ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'null) from t1, t2' at line 1
+ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'not null) from t1, t2' at line 1
 drop table t1,t2,t3;
 CREATE TABLE t1 (id INT);
 CREATE TABLE t2 (id INT);
@@ -5003,7 +5003,7 @@ CREATE VIEW v2 (a,b) AS
 SELECT t2.id, t2.c AS c FROM t1, t2
 WHERE t1.id=t2.id AND 1 IN (SELECT id FROM t1) WITH CHECK OPTION;
 INSERT INTO v2(a,b) VALUES (2,2);
-ERROR HY000: CHECK OPTION failed 'test.v2'
+ERROR HY000: CONSTRAINT 'WITH CHECK OPTION' failed for 'test.v2'
 SELECT * FROM v1;
 c
 1