clutter-group: Use g_list_foreach in clutter_group_real_foreach
clutter-group: Use g_list_foreach in clutter_group_real_foreach

g_list_foreach has better protection against the current node being
removed. This will happen for example if someone calls
clutter_container_foreach(container, clutter_actor_destroy). This was
causing valgrind errors for the conformance tests which do just that.

Distrotech/clutter,djdeath/clutter-multithreaded,Distrotech/clutter,ebassi/clutter,Distrotech/clutter,collects/clutter,rkudiyarov/clutter_osx,djdeath/clutter,GNOME/clutter,spatulasnout/clutter,rkudiyarov/clutter_osx,jigpu/clutter,collects/clutter,heysion/clutter-clone,djdeath/clutter,collects/clutter,GNOME/clutter,djdeath/clutter-multithreaded,djdeath/clutter-android,djdeath/clutter,kerrickstaley/clutter-vala,spatulasnout/clutter,GNOME/clutter,spatulasnout/clutter,dlespiau/clutter,spatulasnout/clutter,djdeath/clutter-android,GNOME/clutter,djdeath/clutter-android,jigpu/clutter,Distrotech/clutter,ebassi/clutter,kerrickstaley/clutter-vala,Distrotech/clutter,heysion/clutter-clone,ebassi/clutter,ebassi/clutter,jigpu/clutter,Distrotech/clutter,jigpu/clutter,nobled/clutter,collects/clutter,heysion/clutter-clone,kerrickstaley/clutter-vala,djdeath/clutter-multithreaded,GNOME/clutter,djdeath/clutter-multithreaded,jigpu/clutter,djdeath/clutter,jigpu/clutter,collects/clutter,kerrickstaley/clutter-vala,ebassi/clutter,rkudiyarov/clutter_osx,rkudiyarov/clutter_osx,djdeath/clutter,heysion/clutter-clone,djdeath/clutter-android,dlespiau/clutter,djdeath/clutter,dlespiau/clutter,djdeath/clutter-android,nobled/clutter,heysion/clutter-clone,spatulasnout/clutter,nobled/clutter