C++20 standard introduces std::remove_cvref<T>, which allows for a reduction of obfuscator code.
C++20 allows for consteval expressions which force the compiler to only accept compile-time
evaluation of functions. This is especially useful for obfuscating purposes.

* Use macro to use consteval when compiling in C++20 standard, or constexpr for C++14/17.
  Only for those functions which require compile-time evaluation.
* Keep STL independent, because not all users may be willing or able to use the STL in their environment.