surviving drawbridge destruction

From a bug report:  you could end up
standing on water/lava if you survived being on an open drawbridge while
it was destroyed.  This fixes the bridge destruction case; opening and
closing are handled differently and I left them alone.

doc/fixes34.4

@@ -324,6 +324,8 @@ dropped wielded, in use leash should remain in inventory, since it's in-use
 wielded, in use leash can't be snatched by whip-wielding monster
 when using two weapons at once, whip-wielding monster can target either one
 can't #force floor item while engulfed, levitating, or unskilled riding
+if hero or monster standing on opened drawbridge survives its destruction,
+	fall into water or lava instead of remaining on top
 
 
 Platform- and/or Interface-Specific Fixes

src/dbridge.c

@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)dbridge.c	3.5	2006/12/13	*/
+/*	SCCS Id: @(#)dbridge.c	3.5	2007/02/19	*/
 /*	Copyright (c) 1989 by Jean-Christophe Collet		  */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -930,6 +930,11 @@ int x,y;
 #ifdef D_DEBUG
 			pline("%s spared!", E_phrase(etmp1, "are"));
 #endif
+			/* if there is water or lava here, fall in now */
+			if (is_u(etmp1))
+			    spoteffects(FALSE);
+			else
+			    (void)minliquid(etmp1->emon);
 		} else {
 			if (e_inview) {
 			    if (!is_u(etmp1) && Hallucination)