non-moving goal-oriented monsters

Monsters with goals like M3_WANTSBOOK often wouldn't move if another
monster was standing on the the goal object, add code for the missing case

doc/fixes34.0

@@ -427,6 +427,7 @@ make wands of speed or slow monster known if their effect
 	on monsters is observed; likewise for speed boots
 gold detection "materially poor" message inappropriate if you have hidden_gold()
 cannot reflect back an invisible umber hulk or medusa's attack
+monsters with M3_WANTSBOOK often couldn't move in the Wizard-level
 
 
 Platform- and/or Interface-Specific Fixes

src/wizard.c

@@ -355,6 +355,10 @@ tactics(mtmp)
 			    (void) mpickobj(mtmp, otmp);
 			    return(1);
 			} else return(0);
+		    } else {
+			/* a monster is standing on it - cause some trouble */
+			if (!rn2(5)) mnexto(mtmp);
+			return(0);
 		    }
 	        } else { /* a monster has it - 'port beside it. */
 		    (void) mnearto(mtmp, tx, ty, TRUE);