Accessibility: give a message when teleporting a monster

Teleporting a monster only updated the map. Give a message
so blind players can get the same information.
Making a monster invisible gives the same message, if you
cannot detect invisible.
Several other places where monsters teleported themselves
now also give the same message.

src/dig.c

@@ -60,7 +60,7 @@ mkcavepos(xchar x, xchar y, int dist, boolean waslit, boolean rockit)
             return;                   /* don't cover the portal */
         if ((mtmp = m_at(x, y)) != 0) /* make sure crucial monsters survive */
             if (!passes_walls(mtmp->data))
-                (void) rloc(mtmp, TRUE);
+                (void) rloc(mtmp, RLOC_NOMSG);
     } else if (lev->typ == ROOM)
         return;