Add .pbp support to ludo

[bagelbyheart]

This pull request updates ludo to search for games with the .pbp file extension. Coupled with kivutar/ludo-database#4 this would allow people with PlayStation collections stored in the .pbp format to play those games via the built in playlist feature.

[bagelbyheart]

I updated this to further improve multi-disc PlayStation support:

• Added m3u support (it no longer just checks the first rom in the game list)
• Added (Disc *) back to Playlist entries for folks using bin/cue sets.

[bagelbyheart]

This also addresses #502

[bagelbyheart]

My most recent updates should fix the windows build process as well!