Bug 1068116 - [email/POP3] email.js POP3 attachment regressions: binary attachments are corrupted on download and partially downloaded attachments are saved to disk. r=mcav

land https://github.com/mozilla-b2g/gaia-email-libs-and-more/pull/342 in gaia
Merge pull request #24593 from asutherland/email-fix-pop3-attachments

Bug 1068116 - [email/POP3] email.js POP3 attachment regressions: binary attachments are corrupted on download and partially downloaded attachments are saved to disk. r=mcav