support c99 for-loop init decls

tests/tcctest.c

@@ -387,6 +387,10 @@ void loop_test()
     } while (i < 10);
     printf("\n");
 
+    /* c99 for loop init test */
+    for (size_t count = 1; count < 3; count++)
+        printf("count=%d\n", count);
+
     /* break/continue tests */
     i = 0;
     while (1) {