wayland: Immediately destroy wl_* objects when DRM device is authenticated

wayland: Immediately destroy wl_* objects when DRM device is authenticated

The Wayland protocol is only used to determine which device driver to
load and initialize the DRM state. After the initial roundtrips that
open and authenticate the DRM device, the Wayland protocol objects
are not used anymore and will only take up memory and possibly have
events queued that never get handled.
As fix, destroy them immediately after DRM auth is through. This commit
also adds more error checking to the initialization function.

Fixes: #100

Signed-off-by: Philipp Kerling <pkerling@casix.org>