Fix: a number of unblock_points shouldn't unblock unconditionally

Initially diagnosed in an xnethack fuzzer crash - unblock_point
shouldn't be called when a closed door becomes non-closed, because it's
possible that there's a gas cloud on the space which means it still
blocks vision. These always need to be recalc_block_point. A number of
them were fixed, but when I went through all the xnethack ones, I found
some that were unchanged from upstream NetHack. I reproduced the sanity
check impossibles usually by breathing gas at a door as an iron golem
and then opening or destroying the door to trigger the unblock_point
call.

The use of recalc_block_point in wizterrainwish was not triggering this
bug, but the previous code there basically duplicated
recalc_block_point.

src/dig.c

@@ -1435,7 +1435,7 @@ mdig_tunnel(struct monst *mtmp)
         sawit = canseemon(mtmp); /* before door state change and unblock_pt */
         trapped = (here->doormask & D_TRAPPED) ? TRUE : FALSE;
         here->doormask = trapped ? D_NODOOR : D_BROKEN;
-        unblock_point(mtmp->mx, mtmp->my); /* vision */
+        recalc_block_point(mtmp->mx, mtmp->my); /* vision */
         newsym(mtmp->mx, mtmp->my);
         if (trapped) {
             seeit = canseemon(mtmp);