discovered objects within class for a and u

If any artifacts are discovered and menustyle traditional is in use,
the player can type `a to get the artifact subset of discovered items.
Likewise with `u to for unique items (the invocation tools and the
real Amulet).  For normal object classes, `<class> works for every
class, even when there aren't any discoveries for it (where you get
told "you haven't discovered any yet" if you pick such).  But `a
and `u were only allowed if at least one thing in the corresponding
category had been discovered.  Change to allow it even when none have
been.  The feedback of "you haven't discovered any {unique items,
artifacts} yet" was already in place.

Doesn't apply for picking the class via menu.  Menus don't have any
concept of "allowed as a response even though not listed as a choice".

doc/fixes3-7-0.txt

@@ -1,4 +1,4 @@
-NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.838 $ $NHDT-Date: 1646694720 2022/03/07 23:12:00 $
+NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.839 $ $NHDT-Date: 1646953027 2022/03/10 22:57:07 $
 
 General Fixes and Modified Features
 -----------------------------------
@@ -834,6 +834,9 @@ clear obj->bypass for buried objects [a giant on ice triggers a fire trap,
 	rest of giant's dropped inventory, subsequent sanity checks report
 	that there are buried objects which are 'flagged bypass']
 only give Sunsword or Demonbane as starting gear to lawful Angels
+for #knownclass with menustyle=Tradtional, allow player to ask for `a even if
+	no artifacts have been discovered yet, same as `<any-object-class>;
+	likewise for `u to ask to see unique items
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository