Fix: Demogorgon special door dissipation did not recalculate vision

Interestingly, the fuzzer managed to find this issue. It doesn't cause a
crash, just a sanity check failure, but definitely is incorrect
behavior.

While touching this code, I changed the newsym() on the door's space to
feel_newsym() since the message about the door vanishing is not
conditional on being non-blind, and you should be able to tell the door
is now gone even if you are blind.

Author: copperwater

src/lock.c

@@ -212,7 +212,8 @@ picklock(void)
              * conceivably trap themselves in part of the level with no keys to
              * escape with */
             set_door_iron(gx.xlock.door, FALSE);
-            newsym(doorx, doory);
+            feel_newsym(doorx, doory);
+            recalc_block_point(doorx, doory);
             useup(gx.xlock.pick);
             reset_pick();
         }