gitian: upgrade OpenSSL to 1.0.1h

Upgrade for https://www.openssl.org/news/secadv_20140605.txt

Just in case - there is no vulnerability that affects ecdsa signing or
verification.

The MITM attack vulnerability (CVE-2014-0224) may have some effect on
our usage of SSL/TLS.

As long as payment requests are signed (which is the common case), usage
of the payment protocol should also not be affected.

The TLS usage in RPC may be at risk for MITM attacks. If you have
`-rpcssl` enabled, be sure to update OpenSSL as soon as possible.
Merge pull request #4295

6e7c4d1 gitian: upgrade OpenSSL to 1.0.1h (Wladimir J. van der Laan)