Merge branch 'km/imap-send-libcurl-options'

"git imap-send" learned to optionally talk with an IMAP server via
libcURL; because there is no other option when Git is built with
NO_OPENSSL option, use that codepath by default under such
configuration.

* km/imap-send-libcurl-options:
  imap-send: use cURL automatically when NO_OPENSSL defined