Fully implement the CLAP tail extension

Trivial extension, but this required us to be able to send audio thread
callbacks first.

src/wine-host/bridges/clap.h

@@ -69,6 +69,7 @@ struct ClapPluginExtensions {
     const clap_plugin_audio_ports_t* audio_ports = nullptr;
     const clap_plugin_note_ports_t* note_ports = nullptr;
     const clap_plugin_params_t* params = nullptr;
+    const clap_plugin_tail_t* tail = nullptr;
 };
 
 /**