[hacknews] postnews fixed

henry (05/25/82)

Fixed the postnews component of the new news program to (a) standardize
$PATH and (b) use "test" under its own name instead of the "[" synonym
common in post-V7 stuff.  (The "[" usage will be available here sometime,
but I didn't feel like hassling with makefiles and documentation this
afternoon for the sake of one program.)