* Graphics/ES11/Helper.cs:
* Graphics/ES20/Helper.cs:
* Graphics/BindingsBase.cs:
* Platform/X11/GlxHelper.cs:
* Graphics/OpenGL/GLHelper.cs:
* Platform/X11/X11GLContext.cs: Modified BindingsBase to define
abstract GetAddress method (reason: removes OpenTK.Graphics-specific
code from BindingsBase and allows it to be used in different
bindings).
Implemented GraphicsBindingsBase and modified the OpenGL and OpenGL|ES
bindings to use this.
Modified the GLX bindings to inherit from BindingsBase (reason:
reduces code duplication for extension loading).
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).