Investigate difference between gzip/zlib

[LivInTheLookingGlass]

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[LivInTheLookingGlass]

Okay, C++ is making this difference very obvious. C++ will likely support gzip but not zlib initially, as gzip will take less guesswork to implement. For zlib you need to repeatedly guess at the size (from what I can tell in the zlib library).

To determine the size of a gzip encoded text, feed the last four characters in reverse order into unpack_value. This should work for anything <4GiB. If it returns the error code, then the fallback would be to progressively add a bit until things work.