mimics vs DUNGEON_OVERVIEW (trunk only)

Noticed while looking into whether I could use DUNGEON_OVERVIEW data
for something useful, it was recording accurate terrain type for locations
covered by mimics who were mimicking furniture (such as stairs or altars).
Hero should remember the fake terrain rather than whatever is actually
underneath the mimic.

     No fixes entry; user-contributed DUNGEON_OVERVIEW is post-3.4.3 code.

src/dungeon.c

@@ -5,9 +5,6 @@
 #include "hack.h"
 #include "dgn_file.h"
 #include "dlb.h"
-#ifdef DUNGEON_OVERVIEW
-#include "display.h"
-#endif /* DUNGEON_OVERVIEW */
 
 #define DUNGEON_FILE	"dungeon"
 
@@ -2132,7 +2129,7 @@ recalc_mapseen()
 		}
 	}
 
-	/* Update styp with typ if and only if it is in sight or the hero can
+	/* Update lastseentyp with typ if and only if it is in sight or the hero can
 	 * feel it on their current location (i.e. not levitating).  This *should*
 	 * give the "last known typ" for each dungeon location.  (At the very least,
 	 * it's a better assumption than determining what the player knows from
@@ -2147,17 +2144,20 @@ recalc_mapseen()
 	 * Although no current windowing systems (can) do this, this would add the
 	 * ability to have non-dungeon glyphs float above the last known dungeon
 	 * glyph (i.e. items on fountains).
-	 *
-	 * (vision-related styp update done in loop below)
 	 */
 	if (!Levitation)
 		lastseentyp[u.ux][u.uy] = levl[u.ux][u.uy].typ;
 
 	for (x = 0; x < COLNO; x++) {
 		for (y = 0; y < ROWNO; y++) {
-			/* update styp from viz_array */
-			if (viz_array[y][x] & IN_SIGHT)
-				lastseentyp[x][y] = levl[x][y].typ;
+			if (cansee(x, y)) {
+			    struct monst *mtmp = m_at(x, y);
+
+			    lastseentyp[x][y] =
+	    (mtmp && mtmp->m_ap_type == M_AP_FURNITURE && canseemon(mtmp)) ?
+					cmap_to_type(mtmp->mappearance) :
+					levl[x][y].typ;
+			}
 
 			switch (lastseentyp[x][y]) {
 			/*