test: Make glx-based tests depend on glx availability

The gl-device-release, gl-oversized-surface and gl-source-surface
tests use GLX-specific functions to create the GL device, hence they
cannot be used when cairo-gl is enabled without GLX functions.

Transforming them into a GLX specific test fixes a build failure when
GLX is not available.
cgl: Add CoreGL bindings for cairo-gl

CGL (aka CoreGL) is the native GL API on MacOSX, which provides
platform-specific functions to handle the GL context.

It conflicts with GLX, hence if it is enabled GLX is automatically
disabled by configure.
cgl: Update autogenerated files

The Makefile.win32.features files are automatically generated by
./autogen.sh.
Merge branch 'wip/cgl' into wip/coregl