https://cplusplus.github.io/CWG/issues/722.html
nullptr passed to a variadic function now converted to void* in C++.
This does not affect C23 nullptr.
Also fixes -Wformat-pedantic so that it no longer warns for nullptr
passed to %p (because it is converted to void* in C++ and it is allowed
for va_arg(ap, void*) in C23)
