support for calling Linux syscalls directly

[Roland McGrath]

> The approach I proposed was to determine what's "glibc material". I
> suspect everything that's not does not belong in a library at all. If
> the syscall is specific to a single package (like modutils), then the
> package (e.g. modutils) maintainers are going to be a lot more
> competent dealing with the kernel interface than a third party trying
> to maintain libinux.

The plan is that libinux be maintained along with the kernel, which is by
definition the place that knows the kernel interfaces best as they change.