Remove $FreeBSD$: one-line sh pattern

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

sdiff(1) can now be built defaults warning level

Add HAS_TESTS to all Makefiles that are currently using the
`SUBDIR.${MK_TESTS}+= tests` idiom.

This is a follow up to r321912.

Convert traditional ${MK_TESTS} conditional idiom for including test
directories to SUBDIR.${MK_TESTS} idiom

This is being done to pave the way for future work (and homogenity) in
^/projects/make-check-sandbox .

No functional change intended.

MFC after: 1 weeks

Move cleanup() into the edit.c file which is the only users of that function
Remove common.{c,h}

Only one program is build in usr.bin/sdiff use the right include

Replace fparseln(3) with getline(3)

It removes a dependency on libutil.

import sdiff(1) from GSoC 2012

Import sdiff(1) from the diff version written by Raymond Lai,
improved during GSoC 2012 by Jesse Hagewood.

Compared to the version done in during that summer of code:
- Remove the zlib frontend: zsdiff
- Compatible output (column size and separators) with GNU sdiff

Compared to GNU sdiff in ports:
- The only difference is padding using spaces vs tabs

Compared to OpenBSD and NetBSD import:
- Implement missing options (including long options) from GNU sdiff
- Improved support for the edition mode (signal handling)
- Output visually compatible with GNU sdiff: size of columns

While here import regression tests from NetBSD adapted to fit the output as
expected by GNU sdiff

Reviewed by: emaste (in part)
Obtained from: OpenBSD, NetBSD, GSoC 2012
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D5981
Differential Revision: https://reviews.freebsd.org/D6032 (diff with NetBSD version)
Differential Revision: https://reviews.freebsd.org/D6033 (diff with OpenBSD version)

Check in first src/tests snapshot from NetBSD anoncvs

Sources were obtained like so:

% export CVSROOT="anoncvs@anoncvs.NetBSD.org:/cvsroot"
% cvs -z9 co -D "09/30/2014 20:45" -P src/tests
% mv src/tests/* tests/dist/.

'*CVS*' has been added to svn:ignore to ease updating periodically from
upstream

Some line ending issues had to be resolved with test outputs and scripts
via dos2unix and by deleting the eol-style property set in usr.bin/sort

Discussed with: rpaulo
Sponsored by: EMC / Isilon Storage Division