twn_filewatch.c: file and directory change api, initial support for texture reload

src/twn_textures.c

@@ -308,6 +308,8 @@ static void update_texture_rects_in_atlas(TextureCache *cache, stbrp_rect *rects
 
 
 void textures_cache_init(TextureCache *cache, SDL_Window *window) {
+    SDL_zero(*cache);
+
     cache->window = window;
     sh_new_arena(cache->hash);
 
@@ -581,4 +583,6 @@ size_t textures_get_num_atlases(const TextureCache *cache) {
 }
 
 void textures_reset_state(void) {
+    textures_cache_deinit(&ctx.texture_cache);
+    textures_cache_init(&ctx.texture_cache, ctx.window);
 }