dungeon_overview adjustment

The dungeon_overview bits in the rm structure were being
clobbered by a run-length encoding save/restore because
they weren't taken into consideration.

This patch pulls that data out of the rm structure completely.

It also adjusts the run-length encoding checks to take the
candig bit into consideration and adds a comment to rm.h
reminding people to make run-length encoding adjustments
in save.c for any new bits that get added.

src/decl.c

@@ -142,6 +142,11 @@ NEARDATA struct instance_flags iflags = DUMMY;
 NEARDATA struct you u = DUMMY;
 NEARDATA time_t ubirthday = DUMMY;
 
+
+#ifdef DUNGEON_OVERVIEW
+schar lastseentyp[COLNO][ROWNO] = {DUMMY}; /* last seen/touched dungeon typ */
+#endif /* DUNGEON_OVERVIEW */
+
 NEARDATA struct obj *invent = (struct obj *)0,
 	*uwep = (struct obj *)0, *uarm = (struct obj *)0,
 	*uswapwep = (struct obj *)0,