With TIOCSTI supported in pledge "tty proc", csh is good enough to run

With TIOCSTI supported in pledge "tty proc", csh is good enough to run
with pledge "stdio rpath wpath cpath fattr getpw proc exec tty".  (Note
that ksh "emacs mode" is also a abus^Wconsumer of TIOCSTI, but we had
let that slide for a week since noone uses it...)