Rename wingames.lst to gamedesc.txt, and add a couple of extra fields

Rename wingames.lst to gamedesc.txt, and add a couple of extra fields
to it giving each game's "internal" name (as seen in the source file,
.R etc) and also a brief description of the game. The idea of the
latter is that it should be usable as a comment field in .desktop
files and similar.

[originally from svn r9858]