R972 - rust monster eating gold

When !GOLDOBJ, player polymorphed to a rust monster that attempted to eat
gold in the inventory would fail to eat it, but the gold would be consumed
anyway.  Under GOLDOBJ, a later check would work around the invalid prompt.

doc/fixes34.1

@@ -140,6 +140,8 @@ don't allow cursed daggers thrown by monsters to go thru closed doors
 hero polymorphed into an exploding monster should explode when attacking
 	thin air, just like the monster itself
 don't mark holes/trapdoors as seen if you levitate over them while blind
+player polymorphed as rust monster would lose gold in inventory by
+	attempting to eat it, even though the eat failed
 
 
 Platform- and/or Interface-Specific Fixes

src/invent.c

@@ -770,7 +770,9 @@ register const char *let,*word;
 #endif
 
 	/* Equivalent of an "ugly check" for gold */
-	if (usegold && !strcmp(word, "eat") && !metallivorous(youmonst.data))
+	if (usegold && !strcmp(word, "eat") &&
+	    (!metallivorous(youmonst.data)
+	     || youmonst.data == &mons[PM_RUST_MONSTER]))
 #ifndef GOLDOBJ
 		usegold = allowgold = FALSE;
 #else