more mimic-as-boulder (trunk only)

I started to add handling for doorways containing mimic-as-boulder
to doopen() and doclose() as was done for pick_lock(), but decided that
it was better just to prevent mimics from appearing as boulders at closed
door locations in the first place.  So the most recent pick_lock() change
and its fixes entry go away.

     This also fixes a post-3.4.3 bug.  On the top level of Sokoban I
discovered a boulder over a hole; probing reported it as a mimic with
0 hp.  The special level loading code moves mimic-as-boulder away from
trap spots by using place_monster() to put it on another spot, but it
was missing the corresponding remove_monster() to take it away from the
original location so left a stale pointer on the map.

doc/fixes35.0

@@ -70,7 +70,7 @@ when blind and levitating > shouldn't say "stairs" if player has not seen them
 a slow-moving monster hidden under a rotting corpse was not immediately
 	displayed when the corpse rotted away
 mimic that ends up on the rogue level should not mimic a closed door
-mimic should not mimic a boulder while on a pit or hole location
+mimic should not mimic a boulder while on a pit or hole or closed door
 reviving invisible troll could appear visible until it moves
 adjust some of the shop repair messages
 charge for reviving a shop owned corpse or reanimating a shop owned statue
@@ -342,8 +342,6 @@ when reading an unknown scroll and learning it, discovery of teleporation was
 	too late if hero happened to land on another scroll of teleportation
 using an unlocking tool on a closed door which was actually a mimic reported
 	that there was no door to unlock instead of exposing the mimic
-using an unlocking tool on a boulder that was a mimic in a Sokoban doorway
-	successfully unlocked the underlying door without exposing mimic
 
 
 Platform- and/or Interface-Specific Fixes