- bnc598574 has been fixed in upstream commit 8ab137b2bc9630ce20f4
already, so enable c-ares support again.

- Support openSSL compiled without SSLv2 support
- Update to version 7.21.4
* SMTP: add brackets for MAIL FROM
* multi: connect fail => use next IP address
* pubkey_show: allocate buffer to fit any-size result
* Curl_do: avoid using stale conn pointer
* tftpd test server: avoid buffer overflow report from glibc
* OpenSSL get_cert_chain: support larger data sets
* SCP/SFTP transfers: acknowledge speedcheck
* connect problem: use UDP correctly
* OpenSSL: improved error message on SSL_CTX_new failures
* HTTP: memory leak on multiple Location:
* curl.1: typo in -v description
* CURLOPT_SOCKOPTFUNCTION: return proper error code --keepalive-time
* file: add support for CURLOPT_TIMECONDITION
* multi: fix CURLM_STATE_TOOFAST for multi_socket