Allow field_name NOT NULL ENABLED

This is for Oracle compatiblity. ENABLED is in Oracle the default case
and just ensures that the NOT NULL constraints will be tested, which is
also default in MariaDB

sql/sql_yacc.yy

@@ -6555,6 +6555,11 @@ opt_compressed:
         | compressed { }
         ;
 
+opt_enable:
+          /* empty */ {}
+        | ENABLE_SYM { }
+        ;
+
 compressed:
           COMPRESSED_SYM opt_compression_method
           {
@@ -6581,7 +6586,7 @@ compressed_deprecated_column_attribute:
         ;
 
 asrow_attribute:
-          not NULL_SYM
+          not NULL_SYM opt_enable
           {
             Lex->last_field->flags|= NOT_NULL_FLAG;
           }