[glx backend] use FBConfigs instead of Visuals for GL context creation
[glx backend] use FBConfigs instead of Visuals for GL context creation

This replaces calls to the old (glx 1.2) functions glXChooseVisual,
glXCreateContext, glXMakeCurrent with the 1.3+ fbconfig varients
glXChooseFBConfig, glXCreateNewContext, glXMakeContextCurrent.

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