Linux compatibility.

Here is what I promised. Based on the patches in the gentoo repository
http://git.overlays.gentoo.org/gitweb/?p=proj/gamerlay.git;a=tree;f=games-puzzle/polly-b-gone/files;h=b3e98b3e2e0ddda723580088c239d3a949831d69;hb=87ba806773a93ef037407fad690100b8cb391a2b