block: BdrvDirtyBitmap serialization interface

block: BdrvDirtyBitmap serialization interface

Several functions to provide necessary access to BdrvDirtyBitmap for
block-migration.c

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
[Add the "finish" parameters. - Fam]
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 1476395910-8697-9-git-send-email-jsnow@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>