mailarchive.module, obfuscate email addresses in mail body

Issue Summary

To offer better protection against address harvesters, obfuscating mail addresses in the mail body (like, when someone replies to a mail and the mailclient include a line like "john.doe@something.com wrote"...) might be a good idea.

Note this is a very simple pattern, it doesn't cover the whole range of valid rfc2822 addresses

$pattern = '/([\w+.-]+)?@([\w+.-]+)?/';
$obfuscate = '\1@...';
$body = preg_replace($pattern, $obfuscate, $body);

One drawback, it's probably not a good idea to turn this on for mailinglists discussing code (think about php and perl code with lots of @'s in it...)