Fix: hurtling into wall of water

A hero hurtled into a wall of water while levitating, flying, or wearing
water-walking boots wouldn't be stopped by it unless it was on the Plane
of Water.  Make it stop hurtling heroes immediately no matter the
location.

I also noticed that once I was hurtled safely into the wall of water, it
was described as a "pool" when I examined it with ':'.  Fix that, too,
even though I think it shouldn't really be encountered in-game.

src/invent.c

@@ -4218,6 +4218,8 @@ dfeature_at(coordxy x, coordxy y, char *buf)
         cmap = S_lava; /* "molten lava" */
     else if (is_ice(x, y))
         dfeature = ice_descr(x, y, altbuf), cmap = -1; /* "ice" */
+    else if (IS_WATERWALL(ltyp))
+        dfeature = "wall of water";
     else if (is_pool(x, y))
         dfeature = "pool of water";
     else if (IS_SINK(ltyp))