New cyrus-imapd rpms with multi-instance support

[Simon Matter]

I've got a number of requests and patches recently to add multi-instance
support to the Invoca cyrus-imapd rpms. What those implementations didn't
address are the rpm specific aspects of multi-instance handling, like
restarting instances on package update and whatever else.
I ended up with my own implementation which tries to integrate well with
the rpm mechanisms while maintaining compatibility with older releases.
There are two new commands in the distribution, 'add_instance' and
'del_instance', requiring only the instance name as parameter. Instance
name '' is the main instance. To add an instance '2' do

/usr/lib/cyrus-imapd/add_instance 2

edit /etc/imapd2.conf and /etc/cyrus2.conf to fit your needs and start with

service cyrus-imapd2 start

To delete instance '2', do

/usr/lib/cyrus-imapd/del_instance 2

Note: The script will just do what you said - without asking you anything!
      Use with care!

The source rpm is as always here
http://www.invoca.ch/pub/packages/cyrus-imapd/

Since the new feature required a lot of changes I'm very interested to get
feedback on how it works. That's the reason for announcing it here (I
usually don't do that for rpm specific things).

Simon