lock(1): Do not require 'options COMPAT_43' in the kernel config.

lock(1): Do not require 'options COMPAT_43' in the kernel config.

We commented out COMPAT_43 in our configs some time ago, which broke
lock(1) that needed TIOCGETP and TIOCSETP ioctls which are only
available with COMPAT_43.

This commit converts lock(1) to use tcgetattr(3) and tcsetattr(3),
along with some minor cleanups.

Reported-by:  noway on #dragonflybsd
Submitted-by: Joris Giovannangeli <joris@giovannangeli.fr>
Taken-from:   FreeBSD