more PR #1112 - dipping in sinks

Suggestion from entrez:  If dipping something in a sink while hands
are slippery happens to cause that sink to break, only remind player
about still being Glib if the item was '-' or uarmg.

Redo one of the fixes entries:  dipping a potion into a sink does not
dilute it.  The potion is used up and gives a hint about what it does
so player might discover it.

src/fountain.c

@@ -710,7 +710,7 @@ dipsink(struct obj *obj)
         /* can't rely on using sink for unlimited scroll blanking; however,
            since sink will be converted into a fountain, hero can dip again */
         breaksink(u.ux, u.uy); /* "The pipes break!  Water spurts out!" */
-        if (Glib)
+        if (Glib && (!obj || obj == uarmg))
             Your("%s are still slippery.", fingers_or_gloves(TRUE));
         return;
     } else if (obj == &cg.zeroobj || obj == uarmg) {