[label] add a dispose function
[label] add a dispose function

Make sure we destroy the internal ClutterText when the label is disposed.

jonnylamb/mx,pwithnall/mx,jonnylamb/mx,clutter-project/mx,clutter-project/mx,clutter-project/mx,pwithnall/mx,pwithnall/mx,clutter-project/mx,jonnylamb/mx,jonnylamb/mx,pwithnall/mx