Upcoming OpenSSL 1.1.0 will break compilation b updating a few APIs
we use in imap-send, which has been adjusted for the change.
* ky/imap-send-openssl-1.1.0:
configure: remove checking for HMAC_CTX_cleanup
imap-send: avoid deprecated TLSv1_method()
imap-send: check NULL return of SSL_CTX_new()
imap-send: use HMAC() function provided by OpenSSL