Implement {begin|after}-resync-source handlers

These small patches duplicate the resync-target handlers for the other end of the connection.

Some notes:

- I'm not familiar with drbdadm itself, so I'm not sure if the changes to it are sane; I did check and test that the kernel changes are fine and fire the proper callbacks, but was not able to test the drbdadm configuration
- Aborting if the userspace helper exits with non-zero code is done to mirror the before-resync-target helper; but ignoring its result is another choice, if tearing down the connections is deemed to harsh

Iustin Pop (3):
Implement before|after-resync-source in drbdadm Make the drbd driver generate resync-source callbacks Update documentation for resync-source handlers

 documentation/drbd.conf.xml |   27 ++++++++++++++++++++++++++-
 drbd/drbd_worker.c          |   14 ++++++++++++++
 scripts/drbd.conf.example   |    4 ++++
 scripts/global_common.conf  |    2 ++
 user/drbdadm_main.c         |    2 ++
 user/drbdadm_scanner.fl     |    2 ++
 6 files changed, 50 insertions(+), 1 deletions(-)