water vs acid

Fix the bug From a bug report.alt.org server, where killing a monster by closing the
castle drawbridge resulted in a panic after the dead monster's possessions
were dropped into the moat and a potion of acid exploded in the process.
water_damage() deleted the object but had no way to tell flooreffects()
that it was gone, so flooreffects() couldn't tell its own caller not to
place and stack the object.  After that, a chunk of freed memory became
part of the floor objects chain and eventually triggered a panic which
tried to make a save file but whose reason didn't get logged properly.

doc/fixes34.4

@@ -217,6 +217,8 @@ properly handle destruction of equipment carried by monsters hit by
 don't exercize or abuse wisdom when rumors get used for random graffiti
 create_object() created lizard corpses without timers and troll corpses with
 	their revive timers, then changed the corpsenm field
+when a potion of acid was dropped into water and exploded, nethack would
+	continue to use already freed memory and later might panic or crash
 
 
 Platform- and/or Interface-Specific Fixes