box-layout: Make it safe to destroy children from clutter_container_foreach().
box-layout: Make it safe to destroy children from clutter_container_foreach().

Since a call to clutter_actor_destroy() modifies the list of children
it's important to take care while walking the list in a ClutterContainer's
foreach() implementation, otherwise it's impossible to destroy all the
children of a container using clutter_container_foreach() with
clutter_actor_destroy().

This fixes http://bugzilla.clutter-project.org/show_bug.cgi?id=2646

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