pets accompanying ascension or dungeon escape

There was a report recently about "<pet> is still eating" coming out
on the console at end of game for player using X11 or Qt.  That happened
because the end-of-game pet handling takes place after the message window
has been closed.  It won't happen with the dev code any more because eating
no longer prevents pets from accompanying on final ascent or escape.  But
a pet carrying the Amulet should still fail to tag along and yield similar
result.  However, levl_follower() was changed (probably by me...) to have
pets not attempt to follow when they carried the Amulet, rendering code
in keepdogs()--which reported them as being confused--unreachable.  This
reverts levl_follower() to have Amulet-carrying monsters other than the
Wizard try to accompany the hero during level changes (and keepdogs still
prevents them from succeeding).  It also reorganizes keepdogs() a bit,
giving trapped followers an extra chance to escape from their trap and
preventing those who fail that chance from tagging along (previously,
non-pets ignored being trapped).

     After doing that, I got tty to behave similarly to the X11/Qt report:
a message behaved strangely.  In my case, it was delivered between a pair
of clearings of the screen and only visible by using terminal emulator's
scrolling buffer.  I think there's a wait_synch() missing somewhere, but
haven't tried to figure out where.  Instead, this makes the end-of-game
call to keepdogs() take place sooner, while pline() still works normally.

doc/fixes34.4

@@ -101,6 +101,7 @@ avoid giving extra information about things that break out of sight
 avoid giving away wand type for near misses while blind
 avoid excessive repetition of "monsters are aware of your presence"
 monster's aggravation spell now affects meditating monsters
+handle pets sooner at end-of-game to avoid message delivery anomalies
 busy pet won't miss out upon ascension
 fix various places that "finally finished" could be displayed after the hero
 	stopped doing something other than eating