howto documentation

[Harold Hunt]

Suhaib> We use Cygwin-xfree, Cygwin/XFree and Cygwin/Xfree

I have replaced all direct references in the How-To SGML source to the names
of the Cygwin project, the Cygwin/XFree86 project, and the XFree86 project
with global variables.  I have also defined all referenced URLs as global
variables.

I believe it is important to use a constant name for all project references,
so I'm doing my part.  :)

Harold