poll workers for non-threaded support, emscripten main loop, remove twn_model.c

src/twn_textures.c

@@ -466,7 +466,7 @@ static TextureKey textures_load(TextureCache *cache, const char *path) {
     SDL_UnlockMutex(textures_load_mutex);
 
     /* signal work to do */
-    SDL_SemPost(workers_job_semaphore);
+    workers_add_job();
 
     cache->is_dirty = true;