krb5-1.12 - New iprop features - tree propagation & slave notify

[Richard Basch]

I cleaned up the commits (especially since I found an error in one of my man
page updates).

Wiki:
https://github.com/rbasch/krb5/wiki/Replication-enhancements

Within the wiki, it lists the commits:
https://github.com/rbasch/krb5/commit/0f4b84669c345cb81e60b26372fa32bb9834c0
93 (ulog tracking on slaves)
https://github.com/rbasch/krb5/commit/023602cc7934c96ab7130aa194812289584737
49 (tree propagation feature)
https://github.com/rbasch/krb5/commit/de078a1f49a8d40ba5a5cb7fdbe22c593f3050
9a (slave notification)

A summary view is available via:
https://github.com/rbasch/krb5/compare/krb5-1.12

For anyone just joining in the discussion, I enhanced the replication
strategy so a tree-based hierarchy can be setup (useful for improving
scale-out and for sites where multiple servers may be across slow WAN
links). In addition, when updates are registered in the database, notify
events are sent to iprop slave servers so they know there are pending
updates (which reduces replication lag). The exact methodology is described
in the wiki.

The patches have already been tested with the final 1.12 production release
(they were previously tested against the 1.12 beta releases).