DRM is available on more platforms than Linux (e.g. kFreeBSD), but
Clutter currently FTBFS there because of not being an alternative to
the __linux__ code (where it should be HAVE_DRM).
Instead of copying the DRM data structures, we should use libdrm when
falling back to directly requesting to wait for the vblank.
http://bugzilla.clutter-project.org/show_bug.cgi?id=2225
Based on a patch by: Emilio Pozuelo Monfort <pochu27@gmail.com>
Signed-off-by: Emmanuele Bassi <ebassi@linux.intel.com>