The session_handle class exposes the same public interface to session_impl as
the session class. The difference being that session_handle does not own the
underlying session_impl so multiple session_handle instances can be created
and copied about as needed.
The intent is to chenge the plugin API to pass an instance of session_handle
instead of a pointer to session_impl. This change will be made in a separate
patch.
To maintain ABI compatibilty, the type signature of session was not changed.
The relevent functions have been modified to forward to session_handle and
all enums have been left in session.
Jakob Petsovits