Add missing support for removing foreign data wrapper / server privileges

belonging to a user at DROP OWNED BY. Foreign data wrappers and servers
don't do anything useful yet, which is why no-one has noticed, but since we
have them, seems prudent to fix this. Per report from Chetan Suttraway.
Backpatch to 9.0, 8.4 has the same problem but this patch didn't apply
there so I'm not going to bother.

src/backend/catalog/aclchk.c

@@ -1340,6 +1340,12 @@ RemoveRoleFromObjectACL(Oid roleid, Oid classid, Oid objid)
 			case TableSpaceRelationId:
 				istmt.objtype = ACL_OBJECT_TABLESPACE;
 				break;
+			case ForeignServerRelationId:
+				istmt.objtype = ACL_OBJECT_FOREIGN_SERVER;
+				break;
+			case ForeignDataWrapperRelationId:
+				istmt.objtype = ACL_OBJECT_FDW;
+				break;
 			default:
 				elog(ERROR, "unexpected object class %u", classid);
 				break;