smtp: use eiconv instead of iconv. Add better bounce recognition and is_bulk/is_auto flags for received e-mail.
(cherry picked from commit d0401c929f8439ad00900d317e5b1e0b58f50ad1)
deps: add eiconv as git submodule.
(cherry picked from commit be77327ef116f18478c3eb321894774fd445cac5)
smtp: fix edocs parsing problem on binary notation in comments.
(cherry picked from commit bc3cbc3721bfdc487bf1cd0b85eb75ada1b354e0)
eiconv: fix for warning on linux about missing iconv library.
(cherry picked from commit 795003b78af221184d3b1b268614264b34c870ea)