Removed OpenTK.Graphics.Glu class (reason: deprecated upstream; most functionality provided by OpenTK math; not compatible with OpenGL 3.0+.) OpenTK.Graphics.Glu can be accessed through OpenTK.Compatibility.
Added OpenGL|ES-specific ErrorHelper classes.
Moved OpenTK.Graphics.DisplayDevice and OpenTK.Graphics.DisplayResolution to the root OpenTK namespace (reason: their functionality is not specific and does not depend on OpenTK.Graphics).
Split Graphics*Exception classes into different files.
Made GraphicsErrorException public (reason: necessary for OpenTK.Compatibility).
Replaced all instances of Version14, Version15, Version20, Version30 and Version31 enums by type-safe equivalents.
Added gloverrides.xml to support overrides to function parameters / return types. This will make future spec updates easier to merge.
Improved handling of invalid tokens in the specs.
Bindings are now written in alphabetical order. This will reduce patch size for future updates and make side-by-side comparisons easier to perform.
The doc processor can now document more OpenGL functions (e.g. GL.Color3).
Cleaned up several pieces of code in Bind (but I'm afraid it's hopeless - spaghetti code at its greatest).
