screen width. When built with -DDEBUG, this made the grid bounds checking code
kill the server. Restrict copying to the actual width.
From Kalle Olavi Niemitalo, thanks.
when trying to paste them, found by me, and miscalculation of the start/end
causing random fatal errors when copying in copy-mode, reported by sthen.
ok sthen "put it in" deraadt
terminal to be switched between several different windows and programs
displayed on one terminal be detached from one terminal and moved to another.
ok deraadt pirofti
