i.e. when we have:
{{{
[trac]
never_obfuscate_mailto = true
}}}
the `mailto:user@...` wiki text will always be converted to a visible e-mail address, regardless of any other setting (`[trac] show_email_addresses` or `EMAIL_VIEW` permission).
Of course, this setting defaults to `false`, leaving a site having the default configuration safe w.r.t. #153.
Last minute feature needed for TracHacks ;-)
Closes #8650.
