qapi: Plumb info to the QAPISchemaMember

Future commits will need info in the .check() methods of
QAPISchemaMember and its descendants.  Get it there.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190927134639.4284-15-armbru@redhat.com>
2 files changed