couple of DUNGEON_OVERVIEW fixes (trunk only)

New hero would remember part of old one's terrain discoveries (such
as presence of fountains) for bones levels.  Also, some topology changes
(such as fountain destruction) can be detected by touch while blinded but
dungeon overview continued to remember the old feature.  Post-3.4.3 code.

src/bones.c

@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)bones.c	3.5	2007/03/01	*/
+/*	SCCS Id: @(#)bones.c	3.5	2007/06/25	*/
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985,1993. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -371,6 +371,9 @@ struct obj *corpse;
 	    levl[x][y].seenv = 0;
 	    levl[x][y].waslit = 0;
 	    levl[x][y].glyph = cmap_to_glyph(S_stone);
+#ifdef DUNGEON_OVERVIEW
+	    levl[x][y].styp = 0;
+#endif
 	}
 
 	fd = create_bonesfile(&u.uz, &bonesid, whynot);