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

	fnnow(clock:clock_t) -> Timespec{
	letmut 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