Hidden holes made by breaking a wand of digging

Holes created via applying a wand of digging were not
shown on the map, because holes are always marked as seen,
and seetrap/feeltrap then do nothing.

src/dig.c

@@ -569,6 +569,7 @@ int ttyp;
 	if (!ttmp) return;
 	newobjs = level.objects[x][y];
 	ttmp->madeby_u = madeby_u;
+	ttmp->tseen = 0;
 	if (cansee(x,y)) seetrap(ttmp);
 	else if (madeby_u) feeltrap(ttmp);