Bump version to 0.5

Also add authors to the AUTHORS file.
Signed-off-by: Aaron Plattner <aplattner@nvidia.com>

AUTHORS

 Stephen Warren
 Aaron Plattner
+Anssi Hannula
+Kiran Pawar

configure.ac

 AC_PREREQ(2.60)
 
-AC_INIT(libvdpau, 0.4.1, [xorg@lists.freedesktop.org], libvdpau)
+AC_INIT(libvdpau, 0.5, [xorg@lists.freedesktop.org], libvdpau)
 AM_INIT_AUTOMAKE([dist-bzip2 foreign])
 AM_MAINTAINER_MODE