Update dummy CREATE ASSERTION grammar

While we are probably still far away from fully implementing
assertions, all patch proposals appear to take issue with the existing
dummy grammar CREATE/DROP ASSERTION productions, so update those a
little bit.  Rename the rule, use any_name instead of name, and remove
some unused code.  Also remove the production for DROP ASSERTION,
since that would most likely be handled via the generic DROP support.

extracted from a patch by Joe Wildish

src/backend/parser/gram.y

@@ -259,11 +259,11 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 		CreateOpFamilyStmt AlterOpFamilyStmt CreatePLangStmt
 		CreateSchemaStmt CreateSeqStmt CreateStmt CreateStatsStmt CreateTableSpaceStmt
 		CreateFdwStmt CreateForeignServerStmt CreateForeignTableStmt
-		CreateAssertStmt CreateTransformStmt CreateTrigStmt CreateEventTrigStmt
+		CreateAssertionStmt CreateTransformStmt CreateTrigStmt CreateEventTrigStmt
 		CreateUserStmt CreateUserMappingStmt CreateRoleStmt CreatePolicyStmt
 		CreatedbStmt DeclareCursorStmt DefineStmt DeleteStmt DiscardStmt DoStmt
 		DropOpClassStmt DropOpFamilyStmt DropPLangStmt DropStmt
-		DropAssertStmt DropCastStmt DropRoleStmt
+		DropCastStmt DropRoleStmt
 		DropdbStmt DropTableSpaceStmt
 		DropTransformStmt
 		DropUserMappingStmt ExplainStmt FetchStmt
@@ -860,7 +860,7 @@ stmt :
 			| CopyStmt
 			| CreateAmStmt
 			| CreateAsStmt
-			| CreateAssertStmt
+			| CreateAssertionStmt
 			| CreateCastStmt
 			| CreateConversionStmt
 			| CreateDomainStmt
@@ -896,7 +896,6 @@ stmt :
 			| DeleteStmt
 			| DiscardStmt
 			| DoStmt
-			| DropAssertStmt
 			| DropCastStmt
 			| DropOpClassStmt
 			| DropOpFamilyStmt
@@ -5639,43 +5638,19 @@ enable_trigger:
 
 /*****************************************************************************
  *
- *		QUERIES :
+ *		QUERY :
  *				CREATE ASSERTION ...
- *				DROP ASSERTION ...
  *
  *****************************************************************************/
 
-CreateAssertStmt:
-			CREATE ASSERTION name CHECK '(' a_expr ')'
-			ConstraintAttributeSpec
+CreateAssertionStmt:
+			CREATE ASSERTION any_name CHECK '(' a_expr ')' ConstraintAttributeSpec
 				{
-					CreateTrigStmt *n = makeNode(CreateTrigStmt);
-					n->trigname = $3;
-					n->args = list_make1($6);
-					n->isconstraint  = true;
-					processCASbits($8, @8, "ASSERTION",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
-
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 							 errmsg("CREATE ASSERTION is not yet implemented")));
 
-					$$ = (Node *)n;
-				}
-		;
-
-DropAssertStmt:
-			DROP ASSERTION name opt_drop_behavior
-				{
-					DropStmt *n = makeNode(DropStmt);
-					n->objects = NIL;
-					n->behavior = $4;
-					n->removeType = OBJECT_TRIGGER; /* XXX */
-					ereport(ERROR,
-							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-							 errmsg("DROP ASSERTION is not yet implemented")));
-					$$ = (Node *) n;
+					$$ = NULL;
 				}
 		;