[SDL] windows in x11 backend (sdl 1.2)

[Ryan C. Gordon]

> Another question is that if there is no good reasons behind this
> three-window system, would the mainstream be interested in a patch
> turning the 1.2 x11 backend into single-window based?

I would be _extremely_ hesitant to apply any more large patches to the 
X11 code in 1.2...it's being rewritten for 1.3, so cleaning something up 
in 1.2 without a clear benefit to most users is asking for trouble.

I didn't write the X11 code in SDL, but as I understand it, every 
strange thing it does was due to some platform, X server, or window 
manager with a unique bug or incompatibility.

--ryan.