fix github issue #483 - map display while engulfed

Report raises two issues:
1) if you perform magic mapping while engulfed (or underwater) the
map got updated and player could view it with cursor+autodescribe,
but when done viewing it did not switch back to the limited engulfed
(or underwater) display.
2) when picking a teleport destination while engulfed/underwater you
have to pick the spot while seeing only the limited view of the map
that is shown while engulfed/underwater.

This fixes #1.  I'm inclined to classify #2 as traditional behavior
and am not going to try to figure out a fix for it.

Fixes #483

src/detect.c

@@ -1334,9 +1334,12 @@ do_mapping(void)
         /* browse_map() instead of display_nhwindow(WIN_MAP, TRUE) */
         browse_map(TER_DETECT | TER_MAP | TER_TRP | TER_OBJ,
                    "anything of interest");
-        docrt();
+        map_redisplay(); /* calls reconstrain_map() and docrt() */
+    } else {
+        /* we only get here when unconstrained is False, so reconstrain_map
+           will be a no-op; call it anyway */
+        reconstrain_map();
     }
-    reconstrain_map();
     exercise(A_WIS, TRUE);
 }