detecting chest and door traps

When confused gold detection finds a door trap or a chest trap, it
puts a bear trap glyph/tile on the map at that location.  (They
disappear once they're within sight.)  Those should be given their
own glyphs so that they can have their own tiles, but this doesn't
do that.  What it does do is describe such fake bear traps as
"trapped door" or "trapped chest" when examined with far-look.
The '^' command--if used while blind so that '^' hasn't disappeared
yet--needs to catch up: it says "I can't see a trap there" when the
adjacent '^' is a fake bear trap.

include/extern.h

@@ -236,6 +236,8 @@ E void NDECL(decl_init);
 
 /* ### detect.c ### */
 
+E boolean FDECL(trapped_chest_at, (int, int, int));
+E boolean FDECL(trapped_door_at, (int, int, int));
 E struct obj *FDECL(o_in, (struct obj *, CHAR_P));
 E struct obj *FDECL(o_material, (struct obj *, unsigned));
 E int FDECL(gold_detect, (struct obj *));