Wait the wayland compositor release the pixmaps before destroying them.

In the case the X server closes, it would still destroy all
pixmaps without waiting the release.

Signed-off-by: Axel Davy <axel.davy@ens.fr>
Remove automatic loading of drm. And makes xwl_drm_pre_init call always work

Signed-off-by: Axel Davy <axel.davy@ens.fr>
drm: Use O_CLOEXEC flag when opening the graphic device.

Signed-off-by: Axel Davy <axel.davy@ens.fr>