redox: add makedev, major, minor, and fix dev_t

[jackpot51]

Description

This adds the makedev, major, and minor functions and fixes the type of dev_t on Redox. These functions are defines in the Redox libc, and are identical to the Linux implementations.

Sources

makedev, major, and minor are defined here: https://gitlab.redox-os.org/redox-os/relibc/-/blob/master/include/sys/sysmacros.h?ref_type=heads. These definitions are directly from musl, which matches the const fns in the libc crate.

The type of dev_t can be seen here: https://gitlab.redox-os.org/redox-os/relibc/-/blob/master/src/platform/types.rs?ref_type=heads#L66. It was recently adjusted to fix a discrepancy between 32-bit and 64-bit Redox systems.

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

[JohnTitor]

Thanks!

[jackpot51]

Can this be backported to 0.2 and released?