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/constraints.result

@@ -1,17 +1,44 @@
 drop table if exists t1;
 create table t1 (a int check (a>0));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL CHECK (a>0)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
 insert into t1 values (1);
 insert into t1 values (0);
+ERROR HY000: CONSTRAINT 'a' failed for 'test.t1'
 drop table t1;
 create table t1 (a int, b int, check (a>b));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  `b` int(11) DEFAULT NULL,
+  CONSTRAINT `CONSTRAINT_1` CHECK (a>b)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
 insert into t1 values (1,0);
 insert into t1 values (0,1);
+ERROR HY000: CONSTRAINT 'CONSTRAINT_1' failed for 'test.t1'
 drop table t1;
 create table t1 (a int ,b int, constraint abc check (a>b));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  `b` int(11) DEFAULT NULL,
+  CONSTRAINT `abc` CHECK (a>b)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
 insert into t1 values (1,0);
 insert into t1 values (0,1);
+ERROR HY000: CONSTRAINT 'abc' failed for 'test.t1'
 drop table t1;
 create table t1 (a int null);
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
 insert into t1 values (1),(NULL);
 drop table t1;
 create table t1 (a int null);