Fixes irssi#733. The fix outlined in irssi#452 had adverse effects for the
following reason. The code removed the restoration path that would go on
the code path from kill SIGTSTP. The problem is this: When Irssi is not
running in a controlling parent (like a shell), the TSTP will in fact be
ignored. In that case, there is no process sending a CONT either and
thus the screen state never gets restored. Luckily, the patch in irssi#457 is
sufficient to prevent the problem in irssi#450 (which lead to the development
of irssi#452). To that end, we do end up with potentially calling
terminfo_cont twice but that is better than not calling it at all.
This reverts commit  b1ffd5f , reversing
changes made to  9cb0419 .