rework favicon storage to use DiskCache

classes/cache/local.php

@@ -2,12 +2,18 @@
 class Cache_Local implements Cache_Adapter {
 	private string $dir;
 
+	public function remove(string $filename): bool {
+		return unlink($this->get_full_path($filename));
+	}
+
 	public function get_mtime(string $filename) {
 		return filemtime($this->get_full_path($filename));
 	}
 
 	public function set_dir(string $dir) : void {
 		$this->dir = Config::get(Config::CACHE_DIR) . "/" . basename(clean($dir));
+
+		$this->make_dir();
 	}
 
 	public function get_dir(): string {
@@ -131,9 +137,6 @@ class Cache_Local implements Cache_Adapter {
 			if ($tmppluginhost->run_hooks_until(PluginHost::HOOK_SEND_LOCAL_FILE, true, $filename))
 				return true;
 
-			$stamp = gmdate("D, d M Y H:i:s", (int)filemtime($filename)) . " GMT";
-			header("Last-Modified: $stamp", true);
-
 			return readfile($filename);
 		} else {
 			return false;