From: Gerd Knorr <kraxel@bytesex.org>

This patch is a v4l2 update.  Changes:

* added new ioctls (VIDIOC_G_PRIORITY, VIDIOC_S_PRIORITY) to give v4l apps
  priorities for tuning and other controls.  Main purpose is that backgrounds
  applictions like nxtvepg which are fishing informations from /dev/vbi
  (teletext, epg, ...) can run at lower priority than interactive tv apps and
  thus the user isn't annonyed with unexpected channel switches.

* add a set of helper functions to handle priorities to the v4l2-common
  module.

* minor fixes in the v4l1-compat module.

* minor header file fixes.