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>

configure.ac

@@ -23,7 +23,7 @@
 # Initialize Autoconf
 AC_PREREQ([2.60])
 AC_INIT([xf86-video-fbturbo],
-        [0.3.1],
+        [0.4.0],
         [https://github.com/ssvb/xf86-video-fbturbo],
         [xf86-video-fbturbo])
 AC_CONFIG_SRCDIR([Makefile.am])