Add 'readable' Hawaiian shirt designs

Functionally similar to reading a T-shirt or apron, but rather than
actual text printed on the shirt being displayed, the design of the
Hawaiian shirt is described: for example, "hula dancers on an orange
background" or "tropical fish on an abstract background".  Much like
T-shirts have their text included in the game-end inventory list ('a
blessed +2 T-shirt with text "foo"'), Hawaiian shirts now have a brief
description of their design appended to their item name under the same
circumstances.

Because 'reading' a Hawaiian shirt doesn't actually involve reading
text, using the 'r' command in this way doesn't break illiterate
conduct.

src/objnam.c

@@ -750,6 +750,10 @@ xname_flags(
             if (*lbl)
                 Sprintf(eos(buf), " labeled \"%s\"", lbl);
             break;
+        case HAWAIIAN_SHIRT:
+            Sprintf(eos(buf), " with %s motif",
+                    an(hawaiian_motif(obj, tmpbuf)));
+            break;
         default:
             break;
         }