crash on hangup

the message history saver needs the windows to stick around until save
is completed.  This usually the case, but end_of_input() was calling
exit_nhwindows prematurely.  This is actually an old bug (calling it early,
but wasn't harmful until other recent changes).

src/cmd.c

@@ -2392,7 +2392,6 @@ static
 void
 end_of_input()
 {
-	exit_nhwindows("End of input?");
 #ifndef NOSAVEONHANGUP
 # ifndef SAFERHANGUP
 	if (!program_state.done_hup++)