Typedef the subtypes of QObject in qemu/typedefs.h, too

Typedef the subtypes of QObject in qemu/typedefs.h, too

This renders many inclusions of qapi/qmp/q*.h superfluous.  They'll be
dropped in the next few commits.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180201111846.21846-8-armbru@redhat.com>