Fix: c99 compliance issue in llex

llex.c

@@ -572,8 +572,9 @@ static int read_command (LexState *ls, SemInfo *seminfo) {
 ** consumed the '}' that closes an interpolated ${expr}.
 */
 int luaX_readcommandcont (LexState *ls) {
+  int tk;
   ls->cmd_mode = ls->saved_cmd_mode;  /* restore mode from before interpolation */
-  int tk = read_command_body(ls, &ls->t.seminfo);
+  tk = read_command_body(ls, &ls->t.seminfo);
   ls->t.token = tk;
   return tk;
 }