Tracker: Allow add-ons to dynamically extend popup menu.

An add-on may now add custom entries to the popup menu, in order
to provide more than one action.

Change-Id: Ib4726c0c1e70c59e3ba4d752df24b76cfee1c4a4

headers/os/add-ons/tracker/TrackerAddOn.h

@@ -7,8 +7,13 @@
 
 struct entry_ref;
 class BMessage;
+class BMenu;
+class BHandler;
 
-extern "C" void process_refs(entry_ref directory, BMessage* refs,
-	void* reserved);
+extern "C" {
+	void process_refs(entry_ref directory, BMessage* refs, void* reserved);
+	void populate_menu(BMessage* msg, BMenu* menu, BHandler* handler);
+	void message_received(BMessage* msg);
+}
 
 #endif	// _TRACKER_ADDON_H

headers/os/app/AppDefs.h

@@ -69,6 +69,7 @@ enum {
 	B_ZOOM						= '_WZM',
 	B_COLORS_UPDATED			= '_CLU',
 	B_FONTS_UPDATED				= '_FNU',
+	B_TRACKER_ADDON_MESSAGE		= '_TAM',
 	_APP_MENU_					= '_AMN',
 	_BROWSER_MENUS_				= '_BRM',
 	_MENU_EVENT_				= '_MEV',