Remove $FreeBSD$: one-line sh pattern

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

Convert freebsd-version to using -v

newvers.sh has supported a variable setting only mode, use that in
preference to grep to future proof this script from changes there.

Differential Revision: https://reviews.freebsd.org/D19849

bin: normalize paths using SRCTOP-relative paths or :H when possible

This simplifies make logic/output

MFC after: 1 month
Sponsored by: Dell EMC Isilon

Explicitly add unmarked bin/ binaries to the runtime package.
Note: tcsh(1) has a MK_TCSH=no test, so this should be a separate
package, which requires pre-install/post-install scripts, to be
added later.

Sponsored by: The FreeBSD Foundation

Add missing CLEANFILES.

MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division

Don't include newvers.sh into freebsd-version.

Fix dependency on newvers.sh

Noticed by: marck
MFC after: 1 week

By popular demand, move freebsd-version(1) from /libexec to /bin.

Approved by: re (gjb)