updated lib to cpp20

[Willu12]

Due to changes in template functions, pairing_queue.hpp and util.hpp needed tweaking in order to work with cpp20

[arcondello]

Hi @Willu12 can you say a bit more about what was failing before? With the exception of the

    pairing_node<N>(Args... args) : N(args...), next(nullptr), desc(nullptr) {}

    pairing_node(Args... args) : N(args...), next(nullptr), desc(nullptr) {}

and the inline change most of these changes seem to be stylistic?