Pty ports and TIOCUCNTL mode

[Keith Muller]

Several vendors support TIOCUCNTL, but do not define UIOCMD in ioctl.h which
is why #define JBOOT _IO(u, 1) etc was suggested over UIOCMD, there is no
"rightness" here.

As for sun, TIOCUCNTL does nothing as ptyioctl() in tty_pty.c does not have any
support for it. Almost all of the semantics of TIOCUCNTL is performed by the
TIOCTCNTL ioctl on the sun. There is one major difference: TIOCTCNTL only 
passes some of the 't' ioctls through and not the user defined 'u' ioctls.
(The 't' ioctls alter the slave side and they also appear as the first byte
on the master side with TIOCTCNTL. TIOCUCNTL just passes through to the master
side without no changes to the slave side).
I have patches for tty_pty.c on suns that allow both TIOCUCNTL and TIOCTCNTL to
work.
	Keith Muller
	University of California