[CM] Broken Motif build on OSX

[bil at ccrma.Stanford.EDU]

I think some of the newer Motif packages (like post-2012)
need both /usr/include/X11/extensions/Print.h and
/usr/include/X11/bitmaps/gray -- in the latter case I
sometimes have to create the bitmaps directory.
I can send you copies of these files if needed.

There was a time when everyone was saying Motif was
going away, replaced by gtk, but now it's gtk that
is disliked, and in the background, Motif just
keeps plugging along without any visible support.
So the README.Snd file is a mess.  I'll add this
note about Print.h and gray.

Thanks for the bug report.