[rectangle] Avoid modifying materials mid scene
[rectangle] Avoid modifying materials mid scene

To improve batching of geometry in the Cogl journal we need to avoid modifying
materials midscene.

Currently cogl_set_source_color and cogl_set_source_texture simply modify a
single shared material. In the future we can improve this so they use a pool
of materials that gets recycled as the journal is flushed, but for now we
give all ClutterRectangles their own private materials for painting with.

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