[mythtv] MythGame in a mixed OS environment

[Greg Estabrooks]

> make sense to only display the roms that are playable on the  
> particular frontend you are using at the time.

 Currently mythgame expects all roms to be available to all frontends
in the same directory structure.

 However it does bring up a good point about making the gameplayers
frontend specific which would in effect affect what gets displayed
in the game tree. I'll have to think this one over for a bit.