* modules/stream_out/switcher.c: New module allowing to replace an MPEG2

* modules/stream_out/switcher.c: New module allowing to replace an MPEG2
  video by a fixed panel (format .uyvy). Specify panel files with
  --sout-switcher-files=toto.uyvy,tata.uyvy,titi.uyvy and the size of
  pictures with --sout-switcher-sizes=720x576,720x576,480x576.
  --sout-switcher-port=4242 opens up a UDP port. echo 1 | nc -u localhost 4242
  switches to panel #1 (0 is the live video, -1 disables all output).
  The audio is blanked out when a panel is active. --sout-switcher-command
  specifies the first command to run on start-up.
* modules/access/fake.c: Fake video input simulating a video at x fps.
  Use it to switch between fixed panels with the switcher when you have
  no video.