Allow bitmap successors to carry reference counts.
We can in a later patch use this ability to clean up the dirty bitmap
according to both the individual job's success and the success of all
jobs in the transaction group.
The code for cleaning up a bitmap is also moved from backup_run to
backup_complete.
Signed-off-by: John Snow <address@hidden>
---
block.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++-----
block/backup.c | 20 ++++++----------
include/block/block.h | 10 ++++----
3 files changed, 70 insertions(+), 25 deletions(-)