[clipp] Integrate C++20 compile fix from project's pull request

[DominikGrabiec]

I've got an issue with the clipp library where it does not compile with C++20 and I wanted to submit a pull request for fixing it by using a patch, but on the pull request screen suggested creating an issue to discuss the problem & solution so here I am.

The Problem
Currently the clipp library does not compile with C++20 (at least on Visual Studio 2022) because it uses deprecated functions. There's an open pull request on the project which fixes this but the project itself hasn;'t been updated in many years. (Note I'm not blaming the project owner or expecting anything).

Proposed solution
The patch in the project's pull request works and I've tested it locally by adding it to the ports/clipp/ directory and then referencing it from ports/clipp/portfile.cmake.

This seems like the most light weight solution since we're not forking the project or anything. However I can see potential issues such as incompatability with older C++ standards and other compilers.

Question
So is adding this patch (or some similar patch with more #ifdefs) to fix the C++20 build issue something resonable that vcpkg would want to do or is it outside the scope of this project and people should do that manually?

[Cheney-W]

Normally, this problem should have been fixed by upstream, but it looks like upstream is not maintained anymore, so I think we can add a patch to vcpkg to fix it.