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/os/app/Roster.h

@@ -183,7 +183,9 @@ private:
 									const BList* messageList, int argc,
 									const char* const* args,
 									const char** environment,
-									team_id* appTeam) const;
+									team_id* appTeam,
+									thread_id* appThread,
+									bool launchSuspended) const;
 
 			status_t			_UpdateActiveApp(team_id team) const;