add 'montelecontrol' option (wizard-mode only)

Add a new debugging option, 'montelecontrol', that allows a wizard-
mode player to choose a teleporting monster's destination.  If player
picks a bad spot, confirmation will be requested.  If accepted, the
spot will be used even though the consequences could be bad; that's
on the player.  If rejected, the destination will be assigned as if
no control had been attempted rather than try again.

The fuzzer isn't allowed to override a bad spot if it tries to pick
one.  That would probably trigger a sanity_check warning; the fuzzer
causes impossible warnings to behave as if panic, so accepting a bad
spot would just be fuzzer suicide.  It is allowed to randomly set the
option and maybe--though extremely unlikely--randomly pick a valid
controlled destination.

src/mon.c

@@ -3564,6 +3564,17 @@ mnexto(struct monst *mtmp, unsigned int rlocflags)
         deal_with_overcrowding(mtmp);
         return;
     }
+    /* wizard-mode player can choose destination by setting 'montelecontrol'
+       option; enexto()'s value for 'mm' will be the default; 'savemm' is
+       used to make sure player doesn't choose hero's location and then
+       answer 'y' to the 'override invalid spot' prompt */
+    if (iflags.mon_telecontrol) {
+        coord savemm = mm;
+
+        if (!control_mon_tele(mtmp, &mm, rlocflags, FALSE))
+            mm = savemm;
+    }
+
     rloc_to_flag(mtmp, mm.x, mm.y, rlocflags);
     return;
 }
@@ -3595,6 +3606,7 @@ maybe_mnexto(struct monst *mtmp)
         if (couldsee(mm.x, mm.y)
             /* don't move grid bugs diagonally */
             && (diagok || mm.x == mtmp->mx || mm.y == mtmp->my)) {
+            /* [this doesn't honor the 'montelecontrol' option] */
             rloc_to(mtmp, mm.x, mm.y);
             return;
         }
@@ -3658,6 +3670,7 @@ mnearto(
         newx = mm.x;
         newy = mm.y;
     }
+    /* [this doesn't honor the 'montelecontrol' option] */
     rloc_to_flag(mtmp, newx, newy, rlocflags);
 
     if (move_other && othermon) {