[mythtv] New MPEG2 commercial-cut code ready for testing

[Geoffrey Hausheer]

Well, I finally figured out what was causing the corruption in Bryan's
streams (and likely in Cory's too). Turns out that interlacing wasn't
being enabled properly.
Add the following line around line 950 (right after where c->qmin is set):
 c->flags |= CODEC_FLAG_INTERLACED_DCT;

That is just a hack.  It actually needs to be properly detected, but
I'd like validation that it actually fixes the problem people have had
with ugly images.

.Geoff