[openssl-dev] [openssl.org #3986] [PATCH] Implement HKDF algorithm (RFC 5869)

[Alessandro Ghedini via RT]

Hello,

FYI I rebased the code [0] on master and updated it to use the new test suite
framework. As mentioned in the GitHub PR, I kept the actual implementation and
the tests on two separate commits for easier review, but if you prefer I can
squash them together.

Could someone please review this? Since this is gonna be needed to implement
TLS 1.3 in the future, I don't think there's any objection against merging
this functionality.

Cheers

[0] https://github.com/openssl/openssl/pull/355