[mythtv] Adding support for external ffmpeg-mt library

[Matthew Grant]

Hi!

I am planning to get this happening for 0.22/svn-trunk.

I want to add support for ffmep-mt as an alternate decoder alongside
ffmpeg.  This is so that people can get HD TV viewing functional on
multi-core machines with ATI cards etc.

The idea is to make this a compile time only feature, that can be used
individuals to get HD functional.

I will first do proof of concept against MythTV 0.21-fixes so that any
problems with the ffmpeg-mt libraries are obvious and easier to
resolve. Jean Yves, would you like to help me here.  These will made
available as Development builds for people to try once I have it
running reasonably well to flush anything out.

Second stage is to get this working in svn-trunk.  This is will be the
supported code  for the use of ffmpeg-mt.

I will patching ffmpeg-mt for use with NZ DVB-T.

Regards,

Matthew Grant

PS: Both the UI fixup push and this are for moving svn-trunk forward
so that they are usable.  There are a lot of MythTV users in Norway
and NZ who want to use DVB-T whose needs are not being supported by
the current MythTV development community.