[mythtv] Call for testing switch to public FFmpeg avio API

[Scott Theisen]

Hello all,

I have replaced the last few uses of internal FFmpeg headers and I would 
appreciate some testing.  The changes are here:
https://github.com/MythTV/mythtv/pull/931

I am not aware of any HTTP streams for testing, but playback of 
recordings and videos, making new recordings, and watching live TV all 
worked fine.

Thanks,

Scott