gstplayer: update audio example to test deallocation of gstplayer, as well as loop.
gstplayer: add support for EOS (carefull, EOS is synced, so the event is dispatching within the python GIL + GI lock. You cannot re-enter into Gst, so use Clock to schedule and dispatch EOS.
+ add glib iteration using gstplayer library (not needed for getting events, as we are synced. But i'm not sure of the implication of -not- polling the main glib loop).