Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

bhyveload: Address compiler warnings and bump WARNS

Mostly sprinkle __unused. Also duplicate strings passed to addenv() so
that constant string literals can be passed. No functional change
intended.

Reviewed by: corvink, rew, jhb
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D38840

Move sys/boot to stand. Fix all references to new location

Sponsored by: Netflix

usr.sbin: normalize paths using SRCTOP-relative paths or :H when possible

This simplifies make logic/output

MFC after: 1 month
Sponsored by: Dell EMC Isilon

Fix overlinking in bhyve:

libvmmapi is actually needed to be linked to libutil, not bhyve nor bhyveload

Make FreeBSD-bhyve an indivual package

Convert usr.sbin to LIBADD
Reduce overlinking

Parse the memory size parameter using expand_number() to allow specifying
the memory size more intuitively (e.g. 512M, 4G etc).

Submitted by: rodrigc
Reviewed by: grehan
Approved by: re (blanket)

Add the 'bhyveload(8)' man page.

Obtained from: NetApp
Reviewed by: grehan

'bhyveload' is a userspace FreeBSD loader that can load the kernel + metadata
inside a BHyVe-based virtual machine.

It is a thin wrapper on top of userboot.so which is a variant of the FreeBSD
loader packaged as a shared library. 'bhyveload' provides callbacks that are
utilized by userboot.so to do things like console i/o, disk i/o,
set virtual machine registers etc.

Thanks for Doug Rabson (dfr@) for making this happen.