Dyson

Need portable libnvpair library for userspace.

Userland components should use such a portable library and get rid of sys/nvpair.h.

Since nvpair data are passed to and from the kernel, sys/nvpair.h could only define
such data types, but no functions.

Kernel itself could use other headers for function definitions or such definitions
should be protected with #if defined _KERNEL.

For systems without sys/nvpair.h such a portable library should define
its own, compatible, data types.

See https://github.com/mharsch/libnvpair