[STUMP] preliminary screen wide mode-line

[Shawn Betts]

Hi Folks,

I added the beginninsg of a mode-line like the hardstatus (or whatever
its called) in screen. It's probably buggy and definitely incomplete
but it's there if you wanna play around with it.

there's a command atm "mode-line" the only format option currently
accepted is %w which lists all the windows. You can test it with:

C-t ; mode-line RET some text | %w | some more text RET

-Shawn