patch for multiple addresses with unquoted display parts

[crowbot]

Reduce scope of special case for matching '@' in display name - was matching in case of multiple addresses with unquoted display names. Not a great way to patch but have added test case in case anyone can do a better job.

[ryanbriones]

+1 I'm seeing this as manifested as an email with 2+ CCs parses as a TMail::Mail object with only 1 CC; the last CC. Even though TMail isn't official supported, it seems that this bug should probably be fixed for all the existing Rails 2 codebases out there.