CGL appears to work with both AGL and NSOpenGL contexts, whereas AGL is
limited to AGL contexts. This allows us to be more flexible in terms of
implementation (i.e. we can use Cgl.GetCurrentContext to retrieve a
handle to a context created through SDL, which uses NSOpenGL
internally.)
The IGraphicsMode interface is gradually being removed and the
MacOSFactory will now throw an exception if an instance is requested.
AglContext no longer duplicates MacOSGraphicsMode functionality.
Added IDisposable interface to all classes holding native data that must be freed. OpenTK.Toolkit.Init() now returns an IDisposable instance that can be used to cleanup all native data held by OpenTK. This is useful when re-initializing OpenTK (possibly in a new AppDomain), as is the case in the Example browser.
Added GraphicsContext() constructor that takes an existing, valid OpenGL context. This can be used for interop with third-party toolkits which create the OpenGL context themselves.
Improved CreateDummyContext logic to detect and use the context handle of the current thread or a specified handle.
Removed GetCurrentContext() methods from platform-specific context implementations (everything now goes through the relevant IPlatformFactories).
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.
