digging conjoined pits (trunk only)

This one turned out to be more effort than I had
originally anticipated.

We had a bug report requesting that zapping a wand of digging
laterally while in a pit should dig beside you. That seemed
like a reasonable enough request, but this ended up with
the following results:
- needed to check where this should not be permitted, or at
  least where there should be special-case code because there is
  something such as furniture on the surface above the dig
  point.
- now tracks conjoined pits through new fields in the trap
  structure, hence the pathlevel increment. The array of
  8 boolean values represents each of the 8 directions
  around a pit.
- Previously, pits could be adjacent to each other as two
  individual pits, in which case moving between them
  results in a fall as you went into the next pit. That
  behavior is preserved.
- Pits created either by zapping a wand of digging
  laterally while in a pit, or by "clearing debris"
  between two adjacent pits via a pick-axe, sets the
  conjoined fields for those two pits. You cannot
  create a brand new adjacent pit via pick-axe, only
  with the wand.
- The hero can pass between conjoined pits without
  falling.
- dighole() was hijacked for adjacent pit digging,
  so the ability to pass coordinates to it and
  its downstream functions was added (dig_up_grave()
  for example). dighole() does pretty much everything
  appropriately for this adjacent digging, more so
  than calling digactualhole() directly.
- moving into a conjoined pit that has spikes still
  does damage, but less so that "falling" into the
  spiked pit, and you "step on" the spikes rather
  than falling into them.
- Not done: should pits with the conjoined fields
  set be referred to as 'trenches' rather than pits
  in messages and identifications?

src/hack.c

@@ -915,7 +915,7 @@ domove()
 	register xchar x,y;
 	struct trap *trap;
 	int wtcap;
-	boolean on_ice;
+	boolean on_ice, adj_pit = FALSE;
 	xchar chainx, chainy, ballx, bally;	/* ball&chain new positions */
 	int bc_control;				/* control for ball&chain */
 	boolean cause_delay = FALSE;	/* dragging ball will skip a move */
@@ -1184,7 +1184,10 @@ domove()
 	}
 	if(u.utrap) {
 		if(u.utraptype == TT_PIT) {
-		    climb_pit();
+		    if (trap && trap->tseen &&
+			(trap->ttyp == PIT || trap->ttyp == SPIKED_PIT))
+			adj_pit = TRUE;
+		    if (!adj_pit) climb_pit();
 		} else if (u.utraptype == TT_LAVA) {
 		    if(flags.verbose) {
 			predicament = "stuck in the lava";
@@ -1281,7 +1284,7 @@ domove()
 		    }
 		    if((u.dx && u.dy) || !rn2(5)) u.utrap--;
 		}
-		return;
+		if (!adj_pit) return;
 	}
 
 	if (!test_move(u.ux, u.uy, x-u.ux, y-u.uy, DO_MOVE)) {