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/apply.c

@@ -452,6 +452,7 @@ use_stethoscope(struct obj *obj)
         Soundeffect(se_hollow_sound, 100);
         You_hear(hollow_str, "door");
         cvt_sdoor_to_door(lev); /* ->typ = DOOR */
+        recalc_block_point(rx, ry);
         feel_newsym(rx, ry);
         return res;
     case SCORR: