o Major features (AES performance):
    - When using OpenSSL 1.0.0 or later, use OpenSSL's counter mode
      implementation; it makes AES_CTR about 7% faster than our old one
      (which was about 10% faster than the one OpenSSL used to provide).
      Resolves issue #4526.

  o Major bugfixes (AES performance):
    - Only use the EVP interface when AES acceleration is enabled,
      to avoid a 5-7% performance regression.  Resolves issue #4525,
      bugfix on 0.2.3.8-alpha.