Default option changes-lacking explanation

[Dewayne Geraghty]

It would be very helpful if maintainers could add an explanation for the
changes to default options that they make. 

For example freeradius3 recently added heimdal and updfromto as default
options to the build without any reason in either the maintainer's (svn)
log nor in UPDATING.  As a suggestion:

  * Improved Kerberos support. Added MIT krb as an option. Heimdal base
    now defaults to ON.
  * udp_fromto enables specification of source address, helpful on
    multi-homed devices. Default is now ON

I'm sure there are a lot of administrators that would like to have
consistency in their builds/installs, even if they regularly have to
review the log files to find it.  This is not to take away the valuable
work that maintainers contribute to the project, only that a little more
communication of changes that do affect people will help them to prepare
pro-actively their builds.

Regards, Dewayne.

PS And Zi, thankyou for modernising the Makefile and adding MIT Krb.