Add some documentation about the DRM backend into its own man page, and
refer to it in weston(1).
Environment variable, that are reserved for backends, and currently used
only by the DRM backend, are moved to weston-drm page.
NOTE: This is a candidate for the stable branch
Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
Instead of hardcoding drm-backend.so as the default if environment
presents neither Wayland nor X11, have a ./configure option to change
it. It still defaults to drm-backend.so, if not given.
Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>