Implemented direct binding loading

OpenTK normally uses reflection to load bindings, instead of generating
huge constructors. Although reflection is faster on first load (thanks
to reduced JIT overhead), it fails to work correctly with monolinker.
This branch explores the performance of a direct binding.
Added static GetExtensionDelegate implementation
Moved GetExtensionDelegate to the correct position
Added support for lazy binding loading
Regenerated bindings with lazy loading
Moved delegate loaders to the Delegates class
Generate entry point tables
Add slots into entry point table
Removed delegates and DllImports
Allow overriding of loading methods
Clarified GetAddress documentation
Implemented new loading mechanism
Hooked up new loading mechanism
Hooked up new loading mechanism
Regenerated bindings with new loading mechanism
Removed GLObsolete.cs helper

This file must be recreated using the new loading mechanism.
Moved address parameter to last place

This way, it is the last item on the evaluation stack before calling the
unmanaged function pointer. This simplifies the calli rewrite procedure.
Regenerated bindings
Implemented dll rewriter using Mono.Cecil
Added InteropHelper file