knights and covetous monsters

Implement Pat's suggestion of setting the mavenge flag when a covetous
monster flees, since they may subsequently teleport back and attack even
if mflee is set.

src/wizard.c

@@ -305,6 +305,7 @@ tactics(mtmp)
 	    case STRAT_HEAL:	/* hide and recover */
 		/* if wounded, hole up on or near the stairs (to block them) */
 		/* unless, of course, there are no stairs (e.g. endlevel) */
+		mtmp->mavenge = 1; /* covetous monsters attack while fleeing */
 		if (In_W_tower(mtmp->mx, mtmp->my, &u.uz) ||
 			(mtmp->iswiz && !xupstair && !mon_has_amulet(mtmp))) {
 		    if (!rn2(3 + mtmp->mhp/10)) rloc(mtmp);