[mythtv] [patch] fix for aspect change

[Edward Wildgoose]

> This is a patch which will fix an issue where only aspect ratio is
> changed in a stream, where the previous code would reset a lot of
> unneccesary things, amongs clearing the video buffers. Thanx to Edward
> Wildgoose for providing a small recorded file to play with. I have yet
> to receive a confirmation that it worked for him, but it works nicely
> for me.

Sorry, sat night and lots of recordings all started...  Have tested the patch and it fixes the jittering problem when the aspect
ratio changes

Thanks Kenneth!