[PARSE BUG]: std::nullptr_t

[dvirtz]

Problem description

:1: parse error evaluating 'nullptr_t': unexpected 'nullptr_t', expected 'NAME' or 'operator' or 'template' or 'decltype'

C++ code that can't be parsed correctly (please double-check that https://robotpy.github.io/cxxheaderparser/ has the same error)

void f(std::nullptr_t) {}