Is "Window" really safe as a global typedef name?

I'm looking at the window-functions patch and wondering just what kind
of trouble we'll get into if we leave its new plan node type named just
"Window". I've already confirmed that this is a direct conflict against
a typedef in <X11/X.h>, and I'd be not the least bit surprised if it's
used in even-more-popular system headers on Windows or Darwin. Now
maybe you could always get away with not including such headers together
with plannodes.h, but it sure looks like problems waiting to happen.

So I'm thinking we'd better rename it, but I'm not coming up with
anything good; the best I can do after a long day is "EvalWindow",
and that doesn't seem particularly inspired. Any suggestions?

regards, tom lane