vulnerable items thrown into lava

Reported directly to devteam, player threw a troll corpse into lava and
then later got messages about it reviving and burning to death.  Items
thrown, kicked, or dropped into lava were being subjected to fire damage
(so scrolls burned up, potions boiled, non-fireproofed flammable weapons
and armor eroded), but corpses and a lot of other stuff not subject to
erosion remained unaffected.  This makes things that are made out of
wood, cloth, flesh and other flammable stuff burn up (when in lava, not
when hit by fire).

src/do.c

@@ -190,7 +190,7 @@ const char *verb;
         newsym(x, y);
         return TRUE;
     } else if (is_lava(x, y)) {
-        return fire_damage(obj, FALSE, x, y);
+        return lava_damage(obj, x, y);
     } else if (is_pool(x, y)) {
         /* Reasonably bulky objects (arbitrary) splash when dropped.
          * If you're floating above the water even small things make