Implement the CLAP timer-support extension

This is entirely implemented on the Wine side. I'll assume most Windows
plugins will use their own timers instead, but this could be useful for
plugins that try to use the same interface on all platforms.

src/wine-host/bridges/clap.h

@@ -76,6 +76,9 @@ struct ClapPluginExtensions {
     const clap_plugin_render_t* render = nullptr;
     const clap_plugin_state_t* state = nullptr;
     const clap_plugin_tail_t* tail = nullptr;
+    // Used for the timer-support extension implementation purely on the Wine
+    // side
+    const clap_plugin_timer_support_t* timer_support = nullptr;
     const clap_plugin_voice_info_t* voice_info = nullptr;
 };