std::__binary_function doesn't exist

[limitedAtonement]

I don't see a std::__binary_function here: https://en.cppreference.com/w/cpp/utility/functional/binary_function, and I get a compilation error for std::__binary_function:

../src/database/polyglotdatabase.cpp:25:44: error: expected template-name before ‘<’ token
   25 | struct key_compare : std::__binary_function< const book_entry&, const book_entry&, bool >
      |                                            ^

[themrrobert]

my PR #93 fixes all of these issues. the code is in the progress of updating to qt6, but it needs my PR to simplify compilation.

[limitedAtonement]

Thank you for your note! I'll look at your PR. Are you on the developers' mailing list? https://sourceforge.net/p/chessx/mailman/ I joined and introduced myself a couple days ago, but I haven't seen any activity there. Maybe we should talk there.

What OS do you use?

[limitedAtonement]

Closing in preference to #93.