Add `UINT64_T_ARG` and `INT64_T_ARG` macros for printf arguments, similar to `SIZE_T_ARG` and `PTRDIFF_T_ARG`.
In the process, fix some issues with the toolchain: in certain CI runs the toolchain headers were being #included multiple times, and certain CI runs produced collisions between clang definitions and gcc definitions. Resolve these issues with `#pragma once` and preprocessor guards in the event of both gcc and clang being active.
Also remove toolchain.h from sexp_container.cpp since it is already #included via pstypes.h.
Goober5000
2e65831fa2