Re-implemented SC_WALKSPEED (used in npc scripting) according to official sources (followup to r13037).

git-svn-id: https://svn.code.sf.net/p/rathena/svn/trunk@13039 54d463be-8e91-2dee-dedb-b68131a5f0ec

src/map/status.c

@@ -3781,6 +3781,8 @@ static unsigned short status_calc_speed(struct block_list *bl, struct status_cha
 			speed = 200;
 		if( sc->data[SC_DEFENDER] )
 			speed = max(speed, 200);
+		if( sc->data[SC_WALKSPEED] ) // ChangeSpeed
+			speed = speed * sc->data[SC_WALKSPEED]->val1;
 	}
 
 	return (short)cap_value(speed,10,USHRT_MAX);