Use libc::Ioctl for ioctl constant

[espindola]

Unfortunately musl uses int and glibc uses unsigned long for the ioctl request. The actual kernel sees it as a packed 32 bit value.

The libc crate tests that the symbols it exports have the same signature as the underlying libc. It at least export a Ioctl type that we can use to compile against both glibc and musl without too much pain.

[espindola]

Ping. Anything else I need to do in here?

[jackpot51]

Didn't see this until now. I've reviewed it and asked for a QA review. If QA approves, we will merge and tag a new release.