Update zlib for Linux compilations and make MSToolkit compile on MacOS

[fabianegli]

The make build path did not yet work for zlib-1.3.1

This PR

• updated the Linux build to zlib 1.3.1
• Modifies the Makefile so the build runs on MacOS
• updates unpacked versions of the header files from zlib
• removes obsolete keywords from code which will be compile time errors in C++17 and above.

NB: This the build binaries/libraries have not been thoroughly tested on mac, but it does seem to work:

% ./MSSingleScanSL                  
DESCRIPTION: Reads an MS/MS spectrum from any MSToolkit supported file type and outputs to screen in MS2 format.

USAGE: MSSingleScan [scan number] [file]

[fabianegli]

It would be really nice to have the CI test the builds on PRs. Would that be a welcome addition?

[fabianegli]

NB: Builds on MacOS do not link statically.