* ok - let's start with avifile->ffmpeg morphing

* ok - let's start with avifile->ffmpeg morphing
  for the begining it's major rewrite of asf parsing code
  (tested only inside avifile at this moment)
  it handles descrambling (though without WMA it's probably
  useless inside ffmpeg...
* extended AVStream structure to return information about
  stream time length
* extended AVStream to export  extra data found after standard
  headers - not really usefull for ffmpeg - but Windows codecs
  need them.
* asf parsing is not yet finished but works nicely already
  (at 100% better them before :))

Originally committed as revision 846 to svn://svn.ffmpeg.org/ffmpeg/trunk