fix #1812 - ranged targetting of hidden hero (trunk only)

From a bug report, a hero who had
eaten a mimic corpse and was stuck mimicking gold was hit by an approaching
dragon's breath attack.  Make monsters usually fail to notice that you're
lined up for their ranged attack when/if you're hidden from them.

doc/fixes35.0

@@ -306,6 +306,8 @@ attempting to move direction 'u' as a grid bug performed #untrap command;
 	the other diagonals reported "unknown command" instead of "you can't"
 mimic posing as statue or corpse now picks and maintains particular monst type
 when levitating, don't show '>' as a likely direction for digging
+poly'd or mimicking hero who was hidden from monsters would still be treated
+	as a normal target for their ranged attacks
 
 
 Platform- and/or Interface-Specific Fixes

src/mthrowu.c

@@ -1,4 +1,4 @@
-/*	SCCS Id: @(#)mthrowu.c	3.5	2007/12/17	*/
+/*	SCCS Id: @(#)mthrowu.c	3.5	2009/02/17	*/
 /* Copyright (c) Stichting Mathematisch Centrum, Amsterdam, 1985. */
 /* NetHack may be freely redistributed.  See license for details. */
 
@@ -753,9 +753,16 @@ boolean
 lined_up(mtmp)		/* is mtmp in position to use ranged attack? */
 	register struct monst *mtmp;
 {
-	boolean ignore_boulders = (throws_rocks(mtmp->data) ||
+	boolean ignore_boulders;
-				   m_carrying(mtmp, WAN_STRIKING));
 
+	/* hero concealment usually trumps monst awareness of being lined up */
+	if (Upolyd && rn2(25) &&
+	    (u.uundetected || (youmonst.m_ap_type != M_AP_NOTHING &&
+			       youmonst.m_ap_type != M_AP_MONSTER)))
+	    return FALSE;
+
+	ignore_boulders = (throws_rocks(mtmp->data) ||
+			   m_carrying(mtmp, WAN_STRIKING));
 	return linedup(mtmp->mux, mtmp->muy, mtmp->mx, mtmp->my,
 		       ignore_boulders ? 1 : 2);
 }