[RP] split window updates

[shawn]

So I've updated the frame stuff. There was a race condition with
hiding windows that caused them to be dropped from the window
list. Alas I said to myself, "I'll fix it tomorrow" but when I sat
down the next day I had no idea what the problem was and I couldn't
find it again. So if you find a way to get windows to disappear from
the window list, let me know.

You'll notice windows that are not in a frame or active are
hidden. This makes things a little less confusing and allows you to
concentrate on the window at hand. This sorta breaks transient windows
though, as they become the only window visible and the transient_for
window (the one its attached to) hides. This will be resolved at some
point.

You can now blank a frame by hitting C-t - just like screen.

Hopefully this will make frames a little more stable, but I wouldn't
be surprised if you can find ways to break it...so get hammering!

I haven't yet written any docs on split screen, so if it confuses you
drop by on IRC and someone will probably be able to help you
:). And remember, there's always the source.