Do not reverse bytes for nullvm

[knm3000]

This fixes the following istio proxy test on s390x: https://github.com/istio/proxy/blob/master/test/envoye2e/tcp_metadata_exchange/tcp_metadata_exchange_test.go Resolves https://github.com/proxy-wasm/proxy-wasm-cpp-host/issues/294

[knm3000]

@PiotrSikora @mathetake can you please review? This is a follow-up change for https://github.com/proxy-wasm/proxy-wasm-cpp-host/pull/198. Thanks.

[knm3000]

@PiotrSikora @mathetake would you please review this? Initial big-endian changes have already been merged in https://github.com/proxy-wasm/proxy-wasm-cpp-host/pull/198, but now I'd like to fix null-vm use case. Thanks.

[mathetake]

could you elaborate on what's the error in the test, and how does this solve it?

[knm3000]

@mathetake thanks for the review. I've opened an issue and added the error details https://github.com/proxy-wasm/proxy-wasm-cpp-host/issues/294. Can you please take a look?

[PiotrSikora]

@PiotrSikora @mathetake would you please review this? Initial big-endian changes have already been merged in #198, but now I'd like to fix null-vm use case. Thanks.

Could you add a test that fails without this change? We cannot rely on tests 3 repositories downstream.

[knm3000]

@PiotrSikora thanks for the review, I've made the proposed changes, can you please take a look?

[knm3000]

@PiotrSikora I've made the requested changes:

• Moved the calls to isWasmByteOrder() into htowasm/wasmtoh macros, now it should be removed by preprocessor for non-s390x.
• Added surrounding brackets to htowasm/wasmtoh
• Removed debug leftover can you please review? Thanks.

[knm3000]

@mpwarres thanks for the review, please see my comments.

[mpwarres]

@PiotrSikora and/or @mathetake , I've finished my pass--this now awaits your approval.

[knm3000]

@PiotrSikora I've made the changes, can you please take a look?

[PiotrSikora]

Thanks!