[mythtv] [patch for testing] DVB No Signal

[mian]

DVB seems more robust with bad reception, using the channel up/down
buttons it won't change channels though, just return to the same channel
on some occasions.. but pressing the number to change channels directly
works fine always.

on one occasion watching live tv it somehow skipped back automatically,
hitting pause revealed it jumped back approximately 3:20.. back to the
start I think, hasnt happened since tho.

the backend seems more robust but sometimes you see RemoteReadFile failed
-1 scroll down the screen until you cancel out.

V4L mpeg4 is doing occasional prebuffering pauses now where it wasnt before.