Several minor cleanups improved the man pages of groupmod and groupadd of the shadow project used on most Linux system.s

Gstreamer's asfdemux now handles files with an invalid metadata count of 1 more lenient as older versions of VLC produced such files that otherwise work fine. An accompanied change in VLC was also made so that recent versions create correct files.

A set of additional functions was provided to the cmocka framework to check parameters returning values and ease the checking of errno modifications.