Remove K&R function definitions without prototypes

[Peter-Levine]

With clang-16, -Wdeprecated-non-prototype is set by default and such constructs are errors with -std=c23. This PR updates all affected functions.

Fixes https://github.com/madler/zlib/issues/633

[floppym]

@madler Pushed a similar change to the develop branch yesterday.

[Neustradamus]

Merged commits about K&R removal:

• https://github.com/madler/zlib/commit/5799c14c8526bf1aaa130c021982f831d155b46d
• https://github.com/madler/zlib/commit/e9d5486e6635141f589e110fd789648aa08e9544
• https://github.com/madler/zlib/commit/c4aa356742e03af6670c043905cd2c96f515ad72
• https://github.com/madler/zlib/commit/bf2578be2d0566dc3ee47655d56b62063fe6bae6