Update fs2_open-data

GOG.com's changed the installer _again_ -- and again without announcing
it. Same version number as the first time I updated this package, but a
new md5sum, so that's a pain.

Also I'm deleting a bunch of Windows-centric files that aren't needed on
a Linux port. If you *really* want the *.exe version of the game, install
and play it in Wine!