Fix AddressList toString method to quote semicolon

[glensc]

This is port of zendframework/zend-mail#230 fixing regression from zendframework/zend-mail#147

Fixes #14

---

Certain input of AddressList headers, cannot be converted to string and back to header object because of incorrect quoting:

From: "Foo;" <root@example.com>

gets incorrectly converted as

From: Foo; <root@example.com>

but ; is address separator, so it needs to be quoted:

From: "Foo;" <root@example.com>

The problem I discovered internally when using Storage\Message with Headers input, therefore testing that method is included in the unit test:

$message = new Message(['headers' => new Headers(), 'content' => (string)$body]);

// Mime\Decode::splitMessage calls toString on headers object which creates invalid result:
if ($message instanceof Headers) {
    $message = $message->toString();
}

[glensc]

NOTE: This is needed to switch to laminas-mail in the project I maintain: eventum/eventum#876

[michalbundyra]

@glensc thanks for your contribution. Before we can accept the PR with need DCO to be valid on PRs in Laminas org. Please see https://github.com/laminas/laminas-mail/pull/93/checks?check_run_id=813642578 for more details. Thanks!

[glensc]

@michalbundyra sure, those were fixup commits that I intended to flatten once Travis passed

[michalbundyra]

@glensc would be great, if you can provide another PR with a proper test case for that, thanks!

[glensc]

@michalbundyra what you mean proper? what's wrong with the provided one? please be specific what you mean, test case for what exactly?

[michalbundyra]

@glensc sorry, I mean test with name which contains double quote, so separate issue.

As I understand this is about ; in the name only.

[glensc]

perhaps I remove this "FIXME" comment then it being out of scope? as the changeset does not introduce that as a new problem, the problem was there already before, I just noticed that and left a note.

besides I don't know how it should be encoded and at this point and I'm not interested in researching on, this PR has been waiting to be accepted by upstream way too long to get sidetracked with this.