[Bf-committers] Libavdevice added to ffmpeg

[Benoit Bolsee]

Hi,

The Video Texture module requires the libavdevice library from ffmpeg.
For some reason, it was not installed in extern/ffmpeg. I added it,
taking care to install a version that is consistent with the rest of the
ffmpeg repository (revision 12121 2008-02-15) and modified the
Makefile/Sconscript accordingly.

I hope it works; I don't have a Linux system handy so I can't test. 
Peter, can you have a look to make sure I didn't do wrong things?

/benoit