qcow2: Add two new fields to BDRVQcowState Add two new fields regarding refcount information (the bit width of every entry and the maximum refcount value) to the BDRVQcowState. Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>