Translate the TIOCSBRK & TIOCCBRK ioctl(2)s issued on a pty(4) slave to

Translate the TIOCSBRK & TIOCCBRK ioctl(2)s issued on a pty(4) slave to
corresponding user mode ioctls.

If the master part of the pseudo terminal previously enabled TIOCUCNTL,
it will now receive the TIOCUCNTL_{S,C}BRK commands.  This allows to
send BREAKS commands over a pty(4) independently of the serial terminal
emulator used.

Guidance and ok nicm@, ok ccardenas@, looks ok to deraadt@