[mythtv] MythVideo internal player filetype case sensitive

[Anduin Withers]

> ie can it accept "Internal" as well as "internal" when choosing this
> player or have a "tick box"  or drop down to set this as the value.

In 0.20 Internal was made the default for everything that would work (and
was previously a covered file type).

If multiple player support ever actually gets in, a dropdown/edit will be
there.

The actual change is trivial but so far the only thing MythVideo actually
knows how to do is call the media handler with the name you give it. I'm not
excited about special casing "internal->Internal" there. If typing
"Internal" is too cumbersome, you can also just leave it blank.

-- 
Anduin Withers