Added GameWindowFlags.FixedWindow to allow for fixed border SDL Windows
Changed TranslateFlags to actually translate flags instead of using switch
Made NativeWindow set WindowBorder to Fixed when created with FixedWindow flag like SDL windows
Merge branch 'develop' of git://github.com/Goz3rr/opentk into pr/122
[X11] Improved WindowBorder.Fixed detection

This now works even without having to map the window first.