softlist: restored the support for loading games from compatible
softlists (like gbcolor games in gameboy, and viceversa, msx1
carts in msx2, etc.) by using the syntax
  mess system -media list:gamename 
You can now for instance use again "mess gbcolor -cart gameboy:sml"
to play "Super Mario Land" with the custom palettes of the Game 
Boy Color. [Fabio Priuli]