[Super-tux-devel] add a .desktop entry

[Duarte H. <dua...@my...>]

Hi all, here's a patch to add a .desktop entry so that a menu entry is
created on Gnome, KDE and other XDG-compliant DE's.

It passes make check, and installed the files to the correct locations.
I only tested the installation with "--prefix=$HOME/test" though.
(but tested the .desktop file in the system prefix allright)

Also I'm using data/images/worldmap/tux.png as the icon, it looks good,
but of course, you can use another, or create one.

regards,
Duarte Henriques