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.]

dat/opthelp

@@ -24,6 +24,7 @@ null           allow nulls to be sent to your terminal            [TRUE]
                try turning this option off (forcing NetHack to use its own
                delay code) if moving objects seem to teleport across rooms
 perm_invent    keep inventory in a permanent window               [FALSE]
+pickup_thrown  override pickup_types for thrown objects           [TRUE]
 prayconfirm    use confirmation prompt when #pray command issued  [TRUE]
 pushweapon     when wielding a new weapon, put your previously
                wielded weapon into the secondary weapon slot      [FALSE]