Pre-release version bump to 0.4.0

It makes sense to make a formal release. Providing the
pre-generated 'configure' script should make it less
likely for people to mess with autotools and encounter
troubles:

    https://github.com/ssvb/xf86-video-fbturbo/issues/28
    https://github.com/ssvb/xf86-video-fbturbo/issues/25

Also it's likely that this particular xf86-video-fbturbo
git master snapshot was used in:

    http://www.raspberrypi.org/archives/5580

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>