Prevent the volume slider from stealing the focus

Also decode VP6 in flash ... this currently decodes video upside down (example file: http://samples.mplayerhq.hu/FLV/flash8/harrypotter-480x272-450-vp6.flv ). If someone knows how to tell the vout/codec to change line order ...

FFmpeg now has VP5/VP6 decoding (flash uses special variant with codec id VP6F in ffmpeg ... this isn't used in VLC yet)

(nice reinvention of the while() loop, but I prefer while())

  so that one day we may be able to use IGMPv3/MLDv2 with VLC streams,
* Add recvonly attribute
* Really fix ordering (c= then t= then a=)
* Put type attribute as a session attribute (as per RFC4566)

for nicer Win32 error messages

(not compile tested, but since no one else wanted to do such a boring commit,
 you can't complain)

    + Remove SDP file when bailing out. Patch by Fabrice Ollivier.