[X11] Fixed OnMouseMove being called without mouse movement
[X11] Workaround for issue #146

Windows are now unmapped before being destroyed.
[X11] Fix for issue #143

OpenTK will now use the same GLXFBConfig to create the INativeWindow
and IGraphicsContext on Linux/X11. This resolves an issue where OpenGL
3.x contexts could not be created on some graphics drivers (e.g.
nvidia binary.)
[X11] Fixed GLControl on nvidia binary drivers

Nvidia drivers fail in Glx.MakeCurrent() when using a 32bpp
visual on a window created with a 24bpp visual. Since we do
not know the actual visual until after the context is constructed,
the solution is to implicitly use 24bpp when 32bpp is requested.

The loss of the alpha channel does not have a user-visible effect,
since WinForms do not support translucent windows on X11.
[X11] Use the correct visual info for the context

This also fixes a potential NRE.
Merge pull request #153 from thefiddler/xwindowfix

[X11] INativeWindow fixes