[SAC] new mantra-request mail alias

I've setup a mantra-request alias, currently redirecting
to sysadmin alias, to receive mantra requests from the userid
creation site.

With this move I hope there can be more people helping with
mantra distribution as I'm currently mostly alone in serving
about 3 requests per day.

So, who wants to help with replying to those emails ?
It's a matter of responding (to all, and adding mantra-request in
Reply-To) either asking for more info or granting the mantra,
depending on the email and known status of the user requesting.