sgtty was the original interface to configure terminal attributes on my
UNIX-like operating systems. It has been deprecated by the POSIX termios
interface, which is implemented in almost any modern system.
An advantage of turning this into a binary compatibility interface, is
that we can now eventually remove the COMPAT_43TTY switch from kernel
configurations. This removes many ioctl()'s from the TTY layer.
While there, increase the __FreeBSD_version, which may be useful for the
people working on the Ports tree.
Reviewed by: kib
Approved by: philip (mentor)
e735353f8d