Add macros to enforce not using default printfs

[patrick-gu]

This is my contribution to code quality here.

This ensures that if you try to use a default printf-like function, you will get a compile error.

However, this will only work if you actually included the right printf header, so it might not be that effective. Maybe it could go in a different header?

[celery6]

good for catching cases where you intended to use printf_ (and thus included the header) but just slipped and typed printf. happened to me before.

yeah its not foolproof, but no harm either