[gtkmm] Mutexes

[Leandro Fanzone <leandro hasar com>]

The Glib::Mutex classes are to replace gdk_threads_enter/leave? I mean, 
what mutex should I use to exclude a thread safely with the main GTK 
message queue? In the old fashion, there was a mutex taken automatically 
with each message iteration, so a call gdk_threads_enter() would let me 
in only when the main queue was idle, and thus ensuring I could do GTK 
calls safely from a different thread. How's that achieved these days?
Thank you,

Leandro Fanzone