Fix collectgarbage("count") result if more than 2GB is in use.

Thanks to Tony Finch.

src/lib_base.c

@@ -359,7 +359,7 @@ LJLIB_CF(collectgarbage)
     "\4stop\7restart\7collect\5count\1\377\4step\10setpause\12setstepmul");
   int32_t data = lj_lib_optint(L, 2, 0);
   if (opt == LUA_GCCOUNT) {
-    setnumV(L->top, cast_num((int32_t)G(L)->gc.total)/1024.0);
+    setnumV(L->top, cast_num(G(L)->gc.total)/1024.0);
   } else {
     int res = lua_gc(L, opt, data);
     if (opt == LUA_GCSTEP)