Accessibility: Add location info to messages

Adds a new boolean option, accessiblemsg.  If on, some game messages
are prefixed with direction or location information, for example:

   (west): The newt bites!
   (northwest): You find a hidden door.

I added the info to the most common messages, but several are
still missing it.

src/steal.c

@@ -758,7 +758,7 @@ mdrop_obj(
     }
     /* obj_no_longer_held(obj); -- done by place_object */
     if (verbosely && cansee(omx, omy))
-        pline("%s drops %s.", Monnam(mon), obj_name);
+        pline_xy(mon->mx, mon->my, "%s drops %s.", Monnam(mon), obj_name);
     if (!flooreffects(obj, omx, omy, "fall")) {
         place_object(obj, omx, omy);
         stackobj(obj);