SM3: Add SM3 hash function

SM3 is a secure hash function which is part of the Chinese
"Commercial Cryptography" suite of algorithms which use is
required for certain commercial applications in China.

Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4616)