material: track if material change is layer change
material: track if material change is layer change

We now pass a boolean to _cogl_material_pre_change_notify to know when
a material change is as a result of a layer change. We plan to use this
information to avoid notifying the backends about material changes if
they are as a result of layer changes. This will simplify the handling
of state changes in the backends because they can assume that layer and
material changes are mutually exclusive.

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