change in less for ti_at_:te_at_

as reported by deischen at freebsd.org, ti_at_:te_at_ in termcap for xterms is
no longer working for less.  this is a real pain to us really old farts
here.  in message
<http://lists.freebsd.org/pipermail/freebsd-current/2007-August/075989.html>,
he does suggest a fix.  anyone bribable to review and check this in?

randy