message: Fix ambiguous type comparison in s3_crypto.cc
  tensorflow/contrib/s3/s3_crypto.cc(74): error C2666:
  'std::fpos<_Mbstatet>::operator ==': 3 overloads have similar conversions
  could be 'bool std::fpos<_Mbstatet>::operator ==(std::streamoff) const'
  or 'bool std::fpos<_Mbstatet>::operator ==(const std::fpos<_Mbstatet> &)
  We were seeing this compilation error on Windows builds.
diff: @@ -71,7 +71,7 @@ class S3Sha256OpenSSLImpl : public Aws::Utils::Crypto::Hash {
  SHA256_Init(&sha256);
  auto currentPos = stream.tellg();
  - if (currentPos == -1) {
  + if (currentPos == std::streampos(std::streamoff(-1))) {
  currentPos = 0;
  stream.clear();
  }
  