Add wrappers for some time-related syscalls

[maxbla]

gettimeofday, clock_gettime, clock_settime, clock_getres, nanosleep and clock_nanosleep seem to be supported by various *nixes (at least Linux and FreeBSD), but bindings are not included in this crate.

I'd be happy to open a PR adding these bindings.

[asomers]

Check again. #1281 just added some of those.

[maxbla]

Darn. I must have searched issues and not pull requests. Regardless, some are still not implemented (the original issue has been edited).

[asomers]

Why would you ever use gettimeofday in new code, instead of clock_gettime? And why would you ever need nanosleep instead of thread::sleep?

[maxbla]

My use case is rather niche - I'm instrumenting syscalls, which is quite possibly the only reason to use the first two functions in new code. clock_nanosleep could use a clock other than CLOCK_MONATONIC, which is what std frequently uses (std uses plain nanosleep for thread::sleep).

Do you think it would be worthwhile to at least implement clock_nanosleep?

[asomers]

Do you think it would be worthwhile to at least implement clock_nanosleep?

Yep.