If there are german special chars (Umlaute) in e.g. subject line,
roundup's email notification sends emails with this header field:


######################################################
Reply-To:
=?utf-8?q?Roundup_issue_tracker_T=C3=BCr=3C_email=40example?=@example.com,
     =?utf-8?b?ZmyibnpuYHU+?=@example.com
######################################################


Which is not converted to a human readable output in 'To:'-field by e.g.
MS Outlook while replying.



> test-cases:
> - User making the change has an Umlaut in her realname
> - One and/or more users on the nosy list have Umlaut in their realname
> - maybe you have other cases


In my case neither the sender, nor the recipient have "Umlaute" in their
names.

But my tracker name has an "Umlaut":

"Roundup issue tracker für XYZ"

I've modified the code to try to generate more readable addresses.

r4442