Add noreturn attributes to some error reporting functions

src/pl/plpgsql/src/pl_scanner.c

@@ -528,7 +528,7 @@ plpgsql_scanner_errposition(int location)
  * Beware of using yyerror for other purposes, as the cursor position might
  * be misleading!
  */
-void
+void __attribute__((noreturn))
 plpgsql_yyerror(const char *message)
 {
 	char	   *yytext = core_yy.scanbuf + plpgsql_yylloc;