Change GAMEVERSION define to OpenJK.
Fixes Issue #365.
Tweak GLimp_CompareModes (SDL) in SP to hopefully resolve some compiler warnings in gcc.
Tweak GLimp_CompareModes (SDL) in MP to hopefully resolve some compiler warnings in gcc.
Revert "Tweak GLimp_CompareModes (SDL) in MP to hopefully resolve some compiler warnings in gcc."

This reverts commit 97da035f42471017f71f0a83bb950850201b527e.
Revert "Tweak GLimp_CompareModes (SDL) in SP to hopefully resolve some compiler warnings in gcc."

This reverts commit 79566dd28e378dfcf7b7b61e2fc4200dd2761f5f.
Merge branch 'master' of https://github.com/Razish/OpenJK