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_base.h

@@ -139,6 +139,7 @@ TABLE_LIST *find_table_in_list(TABLE_LIST *table,
                                const char *table_name);
 void close_thread_tables(THD *thd);
 void switch_to_nullable_trigger_fields(List<Item> &items, TABLE *);
+void switch_to_nullable_trigger_fields(Field **info, TABLE *table);
 bool fill_record_n_invoke_before_triggers(THD *thd, TABLE *table,
                                           List<Item> &fields,
                                           List<Item> &values,
@@ -161,7 +162,7 @@ bool setup_fields(THD *thd, Ref_ptr_array ref_pointer_array,
                   List<Item> *sum_func_list, bool allow_sum_func);
 void unfix_fields(List<Item> &items);
 bool fill_record(THD * thd, TABLE *table_arg, List<Item> &fields,
-                 List<Item> &values, bool ignore_errors);
+                 List<Item> &values, bool ignore_errors, bool update);
 bool fill_record(THD *thd, TABLE *table, Field **field, List<Item> &values,
                  bool ignore_errors, bool use_value);