Bug 853659 - [email/activesync] Fix sending mail on Exchange 2007 and lower

This has r+ from @asutherland over at https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/154

Note that the newline changes are because OS X's `sed` is bad, but that will be permanently fixed in the near future (by not using `sed`).