Add vision sanity checking, fix more vision

- Add a vision sanity checking routine

- Recalc block point when digging a door for temporary clouds

- Add recalc_block_point after cvt_sdoor_to_door, because doorways
  on the Rogue level have no doors, and otherwise the sanity checking
  would complain.  This doesn't actually change how the Rogue level
  vision works, as it uses a different vision system

- Monster using a trap in a secret corridor revealed the corridor,
  but didn't unblock the vision unless you saw the location

src/muse.c

@@ -758,8 +758,7 @@ reveal_trap(struct trap *t, boolean seeit)
 
     if (lev->typ == SCORR) {
         lev->typ = CORR, lev->flags = 0; /* set_levltyp(,,CORR) */
-        if (seeit)
-            unblock_point(t->tx, t->ty);
+        unblock_point(t->tx, t->ty);
     }
     if (seeit)
         seetrap(t);