Add 'pickup_stolen' option

Add pickup_stolen option to autopick items stolen from you by a nymph or
monkey, even if they don't match your normal autopickup settings.
Replace was_dropped, was_thrown with a 2-bit bitfield that can contain
values LOST_DROPPED, LOST_THROWN, and LOST_STOLEN (or 0), since they
should all be mutually exclusive anyway as they track the most recent
way the item left the hero's inventory.

[Rebase/merge conflict fixed up.  PR]

dat/opthelp

@@ -50,6 +50,7 @@ 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_stolen  override pickup_types for stolen objects            [True]
 pickup_thrown  override pickup_types for thrown objects            [True]
 pushweapon     when wielding a new weapon, put your previously    [False]
                wielded weapon into the secondary weapon slot