Fix makedev function signature on Apple targets

[nohajc]

Description

Fix the makedev function signature according to actual implementation:
https://github.com/apple-oss-distributions/xnu/blob/8d741a5de7ff4191bf97d57b9f54c2f6d4a15585/bsd/sys/types.h#L154
https://developer.apple.com/documentation/kernel/1547212-makedev

Issue: #4360

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

[rustbot]

r? @tgross35

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[tgross35]

This lgtm, but any reason not to also fix major and minor?

[nohajc]

@tgross35 Oh, right. They're not even using dev_t there. Let me fix it. It's so bizarre...

[nohajc]

Well, I just noticed the functions are only compiled for C++. C still uses those macros which are more loosely defined. Not sure that's reason enough to deviate from the type signatures even if they're questionable.