Added OpenGL 3.0 support for GLX contexts.
Added support for creating dummy contexts (useful if you are creating contexts from an external library).
Cleaned up unused and stale code.
Fixed vsync on X11.
Updated GraphicsContext interface, for better extensibility. Some public functions were moved to IGraphicsContextInternal.
Renamed DisplayDevice.PrimaryDisplay to DisplayDevice.Default.
Updated and documented new GameWindow constructors.
Improved GameWindow.Exit, added GameWindow.ExitAsync() and improved error handling.
Improved GraphicsContext and NativeGLWindow APIs (construction in constructor).
Made ContextHandle public.