This has the following benefits:
* Clearer structure for mirroring
* Slight build time improvement on bundled zlib use (as it only builds once)
* Removes pages of subdir-objects spew from autogen
Circa 2010 to circa 2017.
Retrieved with apt-get source zlib on WSL Ubuntu 18.04.2 LTS.
This matches Debian or Ubuntu (they differ by one commit, and one of them restores a dummy function for compat).
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* [minizip] Ensure we don't ever accidentally change calling convention
Make sure we always #define ZCALLBACK to empty so we don't change
the calling convention on windows by including a header which defines
'CALLBACK'. This will keep things as cdecl as required by the c#
pinvokes.
* Update zlib readme.
* Update zlib from 1.2.5 to 1.2.11.
* [zlib] Small fix for Visual C++.
see https://github.com/madler/zlib/pull/435/files#diff-0558e84b0c24a83ca790dcb05cd26212R1087
and https://github.com/madler/zlib/pull/435/files#diff-0558e84b0c24a83ca790dcb05cd26212R1104
* Add gzguts.h to Makefiles.
* Add .h files to Visual Studio project files just for GUI purposes.