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/suite/innodb/r/innodb-index.result

@@ -544,9 +544,9 @@ t2	CREATE TABLE `t2` (
 delete from t1;
 ERROR 23000: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t4`, CONSTRAINT `dc` FOREIGN KEY (`a`) REFERENCES `t1` (`a`))
 drop index dc on t4;
-ERROR 42000: Can't DROP 'dc'; check that column/key exists
+ERROR 42000: Can't DROP 'dc'; check that constraint/column/key exists
 alter table t3 drop foreign key dc;
-ERROR 42000: Can't DROP 'dc'; check that column/key exists
+ERROR 42000: Can't DROP 'dc'; check that constraint/column/key exists
 alter table t4 drop foreign key dc;
 affected rows: 0
 info: Records: 0  Duplicates: 0  Warnings: 0

mysql-test/suite/innodb/r/innodb-virtual-columns.result

@@ -162,50 +162,42 @@ grad_degree	CREATE TABLE `grad_degree` (
   `plan` varchar(10) NOT NULL,
   `admit_term` char(4) NOT NULL,
   `wdraw_rsn` varchar(4) NOT NULL DEFAULT '',
-  `ofis_deg_status` varchar(15) AS (
-CASE
+  `ofis_deg_status` varchar(15) AS (CASE
 WHEN wdraw_rsn = '' THEN 'In progress'
       WHEN wdraw_rsn = 'DCMP' OR wdraw_rsn = 'TRDC' THEN 'Completed'
       ELSE 'Not Completed'
     END) VIRTUAL,
-  `ofis_deg_status2` varchar(15) AS (
-CASE
+  `ofis_deg_status2` varchar(15) AS (CASE
 WHEN wdraw_rsn = '' THEN 'In progress2'
       WHEN wdraw_rsn = 'DCMP' OR wdraw_rsn = 'TRDC' THEN 'Completed2'
       ELSE 'Not Completed2'
     END) VIRTUAL,
-  `ofis_deg_status3` varchar(15) AS (
-CASE
+  `ofis_deg_status3` varchar(15) AS (CASE
 WHEN wdraw_rsn = '' THEN 'In progress3'
       WHEN wdraw_rsn = 'DCMP' OR wdraw_rsn = 'TRDC' THEN 'Completed3'
       ELSE 'Not Completed3'
     END) VIRTUAL,
-  `ofis_deg_status4` varchar(15) AS (
-CASE
+  `ofis_deg_status4` varchar(15) AS (CASE
 WHEN wdraw_rsn = '' THEN 'In progress4'
       WHEN wdraw_rsn = 'DCMP' OR wdraw_rsn = 'TRDC' THEN 'Completed4'
       ELSE 'Not Completed4'
     END) VIRTUAL,
-  `ofis_deg_status5` varchar(15) AS (
-CASE
+  `ofis_deg_status5` varchar(15) AS (CASE
 WHEN wdraw_rsn = '' THEN 'In progress5'
       WHEN wdraw_rsn = 'DCMP' OR wdraw_rsn = 'TRDC' THEN 'Completed5'
       ELSE 'Not Completed5'
     END) VIRTUAL,
-  `ofis_deg_status6` varchar(15) AS (
-CASE
+  `ofis_deg_status6` varchar(15) AS (CASE
 WHEN wdraw_rsn = '' THEN 'In progress6'
       WHEN wdraw_rsn = 'DCMP' OR wdraw_rsn = 'TRDC' THEN 'Completed6'
       ELSE 'Not Completed6'
     END) VIRTUAL,
-  `ofis_deg_status7` varchar(15) AS (
-CASE
+  `ofis_deg_status7` varchar(15) AS (CASE
 WHEN wdraw_rsn = '' THEN 'In progress7'
       WHEN wdraw_rsn = 'DCMP' OR wdraw_rsn = 'TRDC' THEN 'Completed7'
       ELSE 'Not Completed7'
     END) VIRTUAL,
-  `ofis_deg_status8` varchar(15) AS (
-CASE
+  `ofis_deg_status8` varchar(15) AS (CASE
 WHEN wdraw_rsn = '' THEN 'In progress8'
       WHEN wdraw_rsn = 'DCMP' OR wdraw_rsn = 'TRDC' THEN 'Completed8'
       ELSE 'Not Completed8'