GstCollectPads2 branch

This week I decided to grab the GstCollectPads2 patch (from bug #415754) and start a branch in my freedesktop repository for porting muxers to it. So far we've got:

• oggmux
• avimux
• matroskamux (patch by Mark)
• asfmux
• qtmux

If you always wanted GStreamer to be able to mux subtitles into your movies, now is the time to provide specs/samples/patches for it. And installing from this branch (I try to keep them up-to-date with current git master) and test it a lot in you favorite applications would help to find regressions from the porting process.

Suggestions to improve GstCollectPads2 or other use cases are also welcome.