istream-base64-encoder: Minor fix to require only 3 bytes instead of 4 per input block. Base64 encoder reads 3 bytes and outputs 4 bytes, so it's ok to read only 3 bytes.
istream-base64-encoder: Minor fix to require only 3 bytes instead of 4 per input block.
Base64 encoder reads 3 bytes and outputs 4 bytes, so it's ok to read only 3
bytes.

jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot