ksh: remove broken special handling of test -t

ksh: remove broken special handling of test -t

Drop the vestiges of the pre-POSIX support of `test -t' defaulting to fd
1.  It doesn't work and it always succeed since "-t" is treated as a
string by default when no argument (fd) is specified.

diff by Lucas (lucas [at] sexy [dot] is) with minor change by me.
ok millert@