getentropy() support

Hi,

Would it be possible to add getentropy() to NetBSD? Most major
UNIX OSs have added support for it, NetBSD is currently the only
one I know that doesn't have it. It was introduced by OpenBSD, and
is available in at least FreeBSD, Solaris, Linux and OSX.

The reason for getentropy() is that it's a direct system call, there is
no need to open a file which might not be available in a chroot
for instance.

getentropy() provides the following features:
- It's a high quality CSRNG, intended to be used by a CSRNG in
  userspace.
- It blocks when the kernel CSRNG hasn't been initialized yet.


Kurt