[packman] Can't decode H.264 video after latest gstreamer update to 1.2.0

[Holger Arnold]

> The problem is that some parts update automatically from the main OBS.

Maybe the gstreamer sub-packages should all require a particular major
version of the gstreamer main package.  This would prevent users from
updating gstreamer to a new major version until all installed packages are
actually available in the new version.

        Holger