mail/rainloop: Fix SMTP AUTH PLAIN bug

While I'm here,

• Switch to DISTVERSION
• Pet portclippy
• Re-format Makefile with portfmt

Reference: https://github.com/RainLoop/rainloop-webmail/issues/1629
PR: 257017
Reported by: pi
Obtained from: https://github.com/RainLoop/rainloop-webmail/issues/1629#issuecomment-540398127
MFH: 2021Q4

(cherry picked from commit 09c2f9d63931380306f66bcbef74667502a0c4e0)