feedback from anyone using Policy.sh to be sure nothing is broken by
this change (c1bd23).
+=head2 Stashes are now always defined
+
+%stash:: is now autovivified so 'defined %Foo::' always returns true
+- although calling defined on a stash is now deprecated.
+
=head1 Core Enhancements
XXX New core language features go here. Summarise user-visible core language