Creating a GraphicsContext with null parameters is not a guarantee that
we will get a dummy context that does not call any OpenGL functions. We
need to explicitly define and construct a dummy context that is safe to
use inside the designer.
Affects issue #49
Removed OpenTK.Platform.Utilities.CreateWindowInfo and made the platform-specific CreateWindowInfo methods public (e.g. CreateX11WindowInfo).
Moved Mono Windows.Forms-specific code into X11GLControl.
Removed OpenTK.Platform.Utilities.IsIdle.
Removed obsolete methods from OpenTK.Platform.Utilities.
Marked OpenTK.Platform.Utilities.CreateGraphicsContext as obsolete (use GraphicsContext constructor instead).
Made IWindowInfo implementations private.
