[hacknews] More fixes to ms package

david (12/16/82)

Installed a few new things in the ms macros:
the letter style now does things with no right adjustment or
hyphenation (these seem to be reasonable defaults and were
suggested by Rossana) and the date is right adjusted at the
of the page (if using the letterhead style);
thesis style now behaves properly in the absence of an abstract
(unanticipated originally).