BRoster: Add launchSuspended option to _LaunchApp().

It allows to launch the app, but keep its main thread suspended instead
of automatically resuming it.

Also add appThread argument which allows to retrieve the main thread of
the launched team.

headers/private/app/RosterPrivate.h

@@ -30,9 +30,10 @@ class BRoster::Private {
 
 		status_t Launch(const char* mimeType, const entry_ref* ref,
 					const BList* messageList, int argc, const char* const* args,
-					const char** environment, team_id* appTeam)
+					const char** environment, team_id* appTeam,
+					thread_id* appThread, bool launchSuspended)
 			{ return fRoster->_LaunchApp(mimeType, ref, messageList, argc,
-					args, environment, appTeam); }
+					args, environment, appTeam, appThread, launchSuspended); }
 
 		status_t ShutDown(bool reboot, bool confirm, bool synchronous)
 			{ return fRoster->_ShutDown(reboot, confirm, synchronous); }