treating cron file as a config file

[Vivek Khera]

It has been pointed out to me that the Mailman port stomps over any 
alterations to the cron file when it is upgraded.  I'd like to fix 
this, but I'm unsure how to do it.

Currently, upon install, the port installs the stock cron job file, and 
upon de-install removes that file.

Ideally, we should be able to treat the cron file as we do normal 
config files, but it is not a standard file in the file system since it 
needs to be installed/removed via the crontab utility.

How might I fake this out? I'd appreciate any ideas. Thanks.