more buglist crystal ball detection

<Someone> wrote:
- If I set the 'boulder' option, shouldn't I be able to give the
  symbol I define for them at the crystal ball "object or
  monster symbol" prompt and have it work?
- Could ']' be added as a synonym for 'm', as with genocide?
- set boulder symbol to '3'; use '/' or ';' to examine a
  boulder. Result is "unknown creature causing you disquiet
  co-located with a boulder" even though there's no warning
  glyph '3' there.

src/drawing.c

@@ -612,8 +612,8 @@ void NDECL((*ascgraphics_mode_callback)) = 0;	/* set in tty_start_screen() */
 
 /*
  * Convert the given character to an object class.  If the character is not
- * recognized, then MAXOCLASSES is returned.  Used in invent.c, options.c,
- * pickup.c, sp_lev.c, and lev_main.c.
+ * recognized, then MAXOCLASSES is returned.  Used in detect.c invent.c,
+ * options.c, pickup.c, sp_lev.c, and lev_main.c.
  */
 int
 def_char_to_objclass(ch)