patch to more completely implement SCS stream

Hi list,
        In an effort to track down a bug in scs2pdf, I've been working on
a more complete implementation of the SCS print stream and a
cleanup/documentation of scs.c,h.  I've added some missing functions to
scs.c and documented it to follow the IPDS Technical Reference.  I also
moved things around so that they appear in the same order as the Reference
in order to make things easier to follow.
        I've also changed scs2ascii.c, scs2pdf.c, and scs2ps.c to use
callback functions when they encounter a form feed.  There are other
places where callbacks are needed, but I'm just starting with form feeds
(since there are two form feeds:  normal and required).
        This is the first part of implementation/cleanup/documentation,
but the patch is already big, so I'm doing it in pieces.  The patch is big
enough I don't want to copy it here.  Grab it at:

http://www.chowhouse.com/~james/tn5250.patch

James Rich