container: Add diagnostic warnings for deprecated vfuncs
container: Add diagnostic warnings for deprecated vfuncs

The old add(), remove(), and foreach() virtual functions are deprecated;
ClutterContainer should warn if the public API detects that the vfuncs
have been overridden.

Strictly speaking, it's still legal to override those vfuncs: you can
chain up to the default vtable, or you could just provide an equivalent
implementation. The goal is to avoid having to override the Container
interface, until we can safely deprecate it and remove it in Clutter
2.0.

collects/clutter,collects/clutter,GNOME/clutter,djdeath/clutter,heysion/clutter-clone,jigpu/clutter,GNOME/clutter,djdeath/clutter-android,djdeath/clutter-android,ebassi/clutter,heysion/clutter-clone,djdeath/clutter-multithreaded,collects/clutter,GNOME/clutter,jigpu/clutter,djdeath/clutter-multithreaded,GNOME/clutter,djdeath/clutter-android,Distrotech/clutter,ebassi/clutter,ebassi/clutter,Distrotech/clutter,djdeath/clutter,jigpu/clutter,heysion/clutter-clone,djdeath/clutter-multithreaded,djdeath/clutter,jigpu/clutter,collects/clutter,kerrickstaley/clutter-vala,Distrotech/clutter,collects/clutter,djdeath/clutter-android,Distrotech/clutter,jigpu/clutter,jigpu/clutter,ebassi/clutter,ebassi/clutter,Distrotech/clutter,kerrickstaley/clutter-vala,djdeath/clutter,kerrickstaley/clutter-vala,Distrotech/clutter,djdeath/clutter,heysion/clutter-clone,GNOME/clutter,djdeath/clutter-android,heysion/clutter-clone,kerrickstaley/clutter-vala,djdeath/clutter,djdeath/clutter-multithreaded