[mythtv] Mythtranscode .mpg => .mpg not .mpg => .nuv

[Geoffrey Hausheer]

After lots of help from Cory and Paul, here is a new version of mpeg2parse:
http://www.pblue.org/myth/mpeg2fix-0.5.tgz

It now supports discontiuous PTS, though if an audio frame gets
dropped and the video frame is present, the result may be an A/V
desync.  I haven't seen this happen yet though.

I have also fixed several bugs, including the garbage at the bottom of
inserted frames, and the blockiness that Cory was seeing due to a
custom quantization_matrix.

It is, of course, likely that I added just as many new ones, though
I've been trying to test as well as possible.

I've also included an updated version of mpegparse, which can be a
very useful tool for debugging mpeg2 streams.

The next step in the process is to add support for commercial cutting,
in preparation for getting this tool merged into mythtranscode.  Any
future enhancements (like better insertion algorithms, dealing with
other weird A/V sync issues, etc) will likely wait until after the
code is in merged.

I would, however, like to encourage anyone who has an interest in
getting a stable commercial-cut code sooner rather than later to try
out this version, and give feedback.

.Geoff