[krbdev.mit.edu #7157] krb5-1.10.1 iprop fixes

[Greg Hudson via RT]

We'll need the following (either from Richard or from us as we have time) 
to accept this, per http://k5wiki.kerberos.org/wiki/Contributing_code:

* Each independent change needs to be in a separate patch.
* Automated tests.  This is a little tricky since we don't yet have 
Python tests for incremental propagation.
* Documentation (in the form of changes to doc/rst_source) of the new 
flags and features.

These changes are also substantial enough that we'll need either 
copyright assignment (saying "I assign copyright of these changes to MIT" 
is good enough) or permission to distribute the new code under a BSD-like 
license.