Merge #494: Support OpenSSL versions >= 1.1 for ENABLE_OPENSSL_TESTS

31abd3a Support OpenSSL versions >= 1.1 for ENABLE_OPENSSL_TESTS (Alexander Block)

Pull request description:

  The only reason OpenSSL 1.1 was not supported was the removal of direct
  access to r and s in ECDSA_SIG. This commit adds a simplified version of
  ECDSA_SIG_get0 for < 1.1 that can be used like ECDSA_SIG_get0 in >= 1.1

Tree-SHA512: 7ee49cd8424086bb96968c632b5babce50af98e13c414c4d5028a30fb86896956f829415a92c66387cde57941ab6999b0db823752cb36dd8932d15dd32980763