incremental propagation code

[Ken Raeburn]

Hi.  I've just merged in to the trunk of the MIT krb5 repository some  
changes based on Sun's incremental propagation code.  It should be in  
time for tonight's nightly snapshot.

Sun's code was based on an older release of the MIT code, before the  
Database Abstraction Layer was set up.  So I've had to do a bit of  
work on the code to get it integrated.  There are some rough edges at  
the moment, and some configuration changes from Sun's original  
implementation, which I've tried to document, but I think it's ready  
for some outside testing, if anyone's feeling adventurous.

There are several options that need to be specified in the config  
files of the master and slave for incremental propagation to be  
enabled.  The protocol works by adding a new RPC service, with the  
server in kadmind, and the client side run in kpropd.  Incremental  
changes are passed over the RPC protocol, and if the slave database is  
too far out of date, the slave tells kadmind to fire up kprop to send  
a full database dump, after which incremental propagation is resumed.   
On the master side, all the programs that change the database also  
write their changes to an update log first, so the information can be  
carried to the slaves.

I've made some notes on how to use it in doc/install.texinfo, and some  
other miscellaneous notes and observations in doc/iprop-notes.txt.  If  
you get a chance to try it out in the next 2-3 weeks or so, please let  
me know the results, good or bad....

Ken