Import NetBSD libkvm

Import NetBSD libkvm

Imported with no changes, but not all parts are expected to be
functional.  The libc nlist functionality is enabled for the
purpose of successful linking, although the nlist functionaly has
not been tested on MINIX3 nor is it needed for how we use libkvm.

In terms of function calls: kvm_getproc2, kvm_getargv2,
kvm_getenvv2, and kvm_getlwps are expected to work, whereas
kvm_getproc, kvm_getargv, kvm_getenvv, and kvm_getfiles are not.

Change-Id: I7539209736f1771fc0b7db5e839d2df72f5ac615