Class to manage gl configurations
Class to manage gl configurations

Side effect: Finds a proper visual info (with Render alpha mask) for
transparent windows.

See also

> http://stackoverflow.com/questions/4052940/how-to-make-an-opengl-rendering-context-with-transparent-background/9215724#9215724
> https://github.com/datenwolf/codesamples/tree/master/samples/OpenGL/x11argb_opengl

jotrk/x-choyce,jotrk/x-choyce