Fix test suite on big endian platforms

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Fixes #897

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I forgot endian.h isn't portable so I'll have to take another pass at this at some point.

[JG-Adams]

Question about this, why would checking endian at compile time address it?
If I compile for big-endian what happens if it run on little-endian?
So we're dealing with bitfield. C++ can't make it work on any system???
I though the issue only arise if you're doing things like reinterpret_cast?
I'm curious about this.