Fix system call docs for time::Instant

[ruuda]

The link for UNIX was pointing to the Cloud ABI docs. It should have been pointing to the clock_gettime docs instead. A similar table is repeated in the docs for SystemTime, but there the UNIX entry was already correct.

clock_gettime(CLOCK_MONOTONIC) is the current implementation:

rust/src/libstd/sys/unix/time.rs

Line 274 in 3ebcfa1

Instant { t: now(libc::CLOCK_MONOTONIC) }

rust/src/libstd/sys/unix/time.rs

Lines 348 to 352 in 3ebcfa1

	fn now(clock: clock_t) -> Timespec {
	let mut t = Timespec { t: libc::timespec { tv_sec: 0, tv_nsec: 0 } };
	cvt(unsafe { libc::clock_gettime(clock, &mut t.t) }).unwrap();
	t
	}

r? @steveklabnik

[hanna-kruppe]

Thanks!

@bors r+ rollup

[bors]

📌 Commit 827ee7a has been approved by rkruppe