cogl-xlib: remove special cases for stub winsys
cogl-xlib: remove special cases for stub winsys

Since we no longer have any xlib based backends in Clutter that depend
on the stub winsys in Cogl we can now remove all the special case code
we had for this in cogl-xlib.c

djdeath/cogl,collects/cogl,djdeath/cogl-android,Distrotech/cogl,gcampax/cogl,gcampax/cogl,Distrotech/cogl,djdeath/cogl-android,gcampax/cogl,Distrotech/cogl,spatulasnout/cogl,djdeath/cogl,gcampax/cogl,djdeath/cogl-android,collects/cogl,spatulasnout/cogl,Distrotech/cogl,djdeath/cogl