fix issue with PRIu64 on some compilers, by including sys/types.h early

[AuxLoui]

Fix for #207 (PRIu64 problem)

[thiagomacieira]

Feedback on making commits and making PRs (general, not about this one in particular):

• the commit message should explain why you're making a change. If you have an error message, it's often useful to include it.
• you don't need to explain the what you're changing, because we can read diffs
• the first line of the commit is the "subject" and should be a summary, which we can see in one-line logs (e.g. https://github.com/intel/tinycbor/commits/main/)
• some projects require that you include a signed-off-by footer. We don't insist for TinyCBOR, but I would prefer it is there.
• each commit should be a single, logical/semantic change, which doesn't break the build
• the GitHub PR page is a summary of all commits in the change. If there's only one commit, then just copy the commit message and body (GitHub will do it for you).

[thiagomacieira]

The comment wasn't necessary. But I'll allow it.

However, is this high enough? Imagine something changes in the headers above and breaks? Especially cbor.h, which includes stdint.h.