sys: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

sys: Remove $FreeBSD$: one-line .h pattern

Remove /^\s*\*+\s*\$FreeBSD\$.*$\n/

Add tcgetwinsize(3) and tcsetwinsize(3) to termios

These functions get/set tty winsize respectively, and are trivial wrappers
around corresponding termio ioctls.

The functions are expected to be a part of POSIX.1 issue 8:
https://www.austingroupbugs.net/view.php?id=1151#c3856.
They are currently available in NetBSD and in musl libc.

PR: 251868
Submitted by: Soumendra Ganguly <soumendraganguly@gmail.com>
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D27650