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_load.cc

@@ -399,9 +399,6 @@ int mysql_load(THD *thd,sql_exchange *ex,TABLE_LIST *table_list,
                      set_fields, MARK_COLUMNS_WRITE, 0, 0) ||
         check_that_all_fields_are_given_values(thd, table, table_list))
       DBUG_RETURN(TRUE);
-    /* Add all fields with default functions to table->write_set. */
-    if (table->default_field)
-      table->mark_default_fields_for_write();
     /* Fix the expressions in SET clause */
     if (setup_fields(thd, Ref_ptr_array(), set_values, MARK_COLUMNS_READ, 0, 0))
       DBUG_RETURN(TRUE);
@@ -412,18 +409,8 @@ int mysql_load(THD *thd,sql_exchange *ex,TABLE_LIST *table_list,
 
   table->prepare_triggers_for_insert_stmt_or_event();
   table->mark_columns_needed_for_insert();
-
-  if (table->vfield)
-  {
-    for (Field **vfield_ptr= table->vfield; *vfield_ptr; vfield_ptr++)
-    {
-      if ((*vfield_ptr)->vcol_info->stored_in_db)
-      {
-        thd->lex->unit.insert_table_with_stored_vcol= table;
-        break;
-      }
-    }
-  }
+  if (table->s->virtual_stored_fields)
+    thd->lex->unit.insert_table_with_stored_vcol= table;
 
   uint tot_length=0;
   bool use_blobs= 0, use_vars= 0;
@@ -989,8 +976,7 @@ read_fixed_length(THD *thd, COPY_INFO &info, TABLE_LIST *table_list,
     if (thd->killed ||
         fill_record_n_invoke_before_triggers(thd, table, set_fields, set_values,
                                              ignore_check_option_errors,
-                                             TRG_EVENT_INSERT) ||
-        (table->default_field && table->update_default_fields()))
+                                             TRG_EVENT_INSERT))
       DBUG_RETURN(1);
 
     switch (table_list->view_check_option(thd, ignore_check_option_errors)) {
@@ -1211,10 +1197,10 @@ read_sep_field(THD *thd, COPY_INFO &info, TABLE_LIST *table_list,
     }
 
     if (thd->killed ||
-        fill_record_n_invoke_before_triggers(thd, table, set_fields, set_values,
+        fill_record_n_invoke_before_triggers(thd, table, set_fields,
+                                             set_values,
                                              ignore_check_option_errors,
-                                             TRG_EVENT_INSERT) ||
-        (table->default_field && table->update_default_fields()))
+                                             TRG_EVENT_INSERT))
       DBUG_RETURN(1);
 
     switch (table_list->view_check_option(thd,
@@ -1393,8 +1379,7 @@ read_xml_field(THD *thd, COPY_INFO &info, TABLE_LIST *table_list,
     if (thd->killed ||
         fill_record_n_invoke_before_triggers(thd, table, set_fields, set_values,
                                              ignore_check_option_errors,
-                                             TRG_EVENT_INSERT) ||
-        (table->default_field && table->update_default_fields()))
+                                             TRG_EVENT_INSERT))
       DBUG_RETURN(1);
 
     switch (table_list->view_check_option(thd,