backup terminal title

[perryh at pluto.rain.com]

> I wish to use  the "\033]0;%s\007" sequence in a shell-script to
> set the title of a terminal. But only if I am able to undo it.
>
> My requirement is that this must be done without using anything
> outside the base system.

There is an escape sequence which will cause the terminal to echo
back its current title, but it's a bit tricky to use given only
base-system tools because the echo ends with, IIRC, \007 rather
than \n.  It may be possible in some shells to temporarily set the
line-end character to \007.  You probably also want to (somehow)
cover problematic cases like terminals that don't reply to the
inquiry even though TERMCAP implies that they should.