The syscalls marked as NOSTD are defined in kernel modules that
might be missing on some systems, but are usually present.

Fixes golang/go#27072

Change-Id: Icf9188df85b54872eb80ba73828f35aa578d49aa
Reviewed-on: https://go-review.googlesource.com/129855
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>