More terminal iocctl's need to be PASSTHROUGH?

[Paul Goyette <paul%vps1.whooppee.com@localhost>]

I noticed christos updated the list of PASSTHROGUH IOCCTLs the other 
day, so I figured that might reduce the boucing in/out of compat module.

But it seems that there's more work to do here.  In a xterm window, and 
running tcsh as my shell, simply typing a backspace character causes the 
module to bounce in.

> Module Name:    src
> Committed By:   christos
> Date:           Sun Oct 18 15:58:23 UTC 2015
>
> Modified Files:
>         src/sys/kern: tty.c
>
> Log Message:
> add the pty ioctls to pass through.
>
>
> To generate a diff of this commit:
> cvs rdiff -u -r1.268 -r1.269 src/sys/kern/tty.c



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