Merge branch 'ky/imap-send-openssl-1.1.0' into maint

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

git-compat-util.h

@@ -279,9 +279,6 @@ extern char *gitdirname(char *);
 #endif
 #include <openssl/ssl.h>
 #include <openssl/err.h>
-#ifdef NO_HMAC_CTX_CLEANUP
-#define HMAC_CTX_cleanup HMAC_cleanup
-#endif
 #endif
 
 /* On most systems <netdb.h> would have given us this, but