hangup revisited (trunk only)

More SAFER_HANGUP tweaking.  Delay its kicking in until main command
loop has been reached, and shut if off again once program is terminating.

sys/vms/vmsmain.c

@@ -375,9 +375,6 @@ byebye()
 	    hup != (void FDECL((*),(int))) SIG_DFL &&
 	    hup != (void FDECL((*),(int))) SIG_IGN) {
 	(*hup)(SIGHUP);
-#ifdef SAFERHANGUP
-	end_of_input();
-#endif
     }
 
 #ifdef CHDIR