sdiff: Fix binary case.

MFC after: 1 week
Sponsored by: Klara, Inc.
Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D43942

sdiff: Fix --expand-tabs and --tabsize.

MFC after: 1 week
Sponsored by: Klara, Inc.
Reviewed by: markj
Differential Revision: https://reviews.freebsd.org/D43941

Remove $FreeBSD$: one-line sh pattern

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

Rename tests from <foo> to <foo>_test to match the FreeBSD test suite
naming scheme

usr.bin/diff/diff_test was renamed to usr.bin/diff/netbsd_diff_test
to avoid collisions with the renamed FreeBSD test.

MFC after: 1 week
Sponsored by: Dell EMC Isilon