Bug 1091295 - [email] normalize newlines in composer. r=jrburke

land https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/352

Failure to normalize newlines in composed messages. May cause some SMTP servers
(ex: qmail) to refuse to send mail with a 451 error.
Merge pull request #25951 from asutherland/email-compose-normalize-newlines

Bug 1091295 - [email] normalize newlines in composer. r=jrburke