Request to rename version.h

Dear developers,

I would like to request renaming the file version.h (and potentially
version.c) to something else, for example gnuplot_version.h.

The problem is that C++20 introduced a standard header version.h:
    https://en.cppreference.com/w/cpp/header/version
which is now causing issues when using a C++20-compliant compiler for gnuplot.

We need to patch gnuplot we ship inside a package manager as soon as
possible, but ideally I would like to use the same patch as upstream.

Thank you very much,
    Mojca