[vlc-devel] Add v4l2 output module

[Francois Cartegnie]

Here's a V4L2 output module.

It is mostly indented to be used/and have been tested with the linux
v4l2loopback module (can be used to fake a v4l2 webcam or use a dv cam).

The usual way was to redirect the YUV vout into a fifo and then a v4l2 writer.

Unfortunately, some apps (skype, flash, ...) won't work with YUV or will require
a custom size. On the performance side, all current implementations were based
on device I/O only.

This module outputs in a negociated format, and tries to use mmap.
To make things even easier, applications profiles can be used to configure
output format/size.

With luck it should also work with regular v4l2 output devices (non mpeg stream).

Francois