add pickup_thrown option (trunk only)

This patch by <email deleted> was released
when 3.4.1 was current and has been incorporated into slash'em.  It is
extremely useful while using ranged weapons.  When both autopickup and
pickup_thrown are enabled, walking across previously thrown objects will
pick them up even if they don't match the current pickup_types list.
[See cvs log for patchlevel.h for longer description.]

src/invent.c

@@ -298,6 +298,7 @@ struct obj *obj;
 	if (obj->where != OBJ_FREE)
 	    panic("addinv: obj not free");
 	obj->no_charge = 0;	/* not meaningful for invent */
+	obj->was_thrown = 0;	/* ditto */
 
 	addinv_core1(obj);
 #ifndef GOLDOBJ