. First draft for ffmpeg - Video For Linux support

    The purpose is to be able to stream and compress in real-time
    video from a video4linx device (webcam, tuners...)

  . New modules :
    - v4linput
    - v4lreader : ioctl for using the video4linux API
    - raw2ts : converts raw frames into TS packets

      V4Lreader -> Raw frames -> ffmpeg -> ES -> PES -> TS
                                 \-------raw2ts----------/

      PTS and PCRs are regenerated using the system clock....
      but it works quite well !

  . To compile :
    % ./configure --enable-v4l --with-ffmpeg=/usr/src/ffmpeg for example

  . To be improved :
    - Support for others webcams & implements ioctl for TV tuners
    - Improve the PES header / TS header / PTS / PCR generation
    - Generate real PAT & PMT using libdvbpsi
    - More parameters like quality/bitrate, image size
      (quality is defined by m_CodecContext->qmax and qmin)
    - stabilize

  . Tested :
    - Philips 730 webcam with vlc 0.4.6.