[Xlibs] Shared library support on Cygwin

[Keith Packard]

Around 0 o'clock on Jan 14, Jim Gettys wrote:

> Possibly/probably we could remove it; it wouldn't be the first time that
> X libraries were linked against libraries unnecessarily.

Nope; Xlib uses a few Xau routines.  When I did this at MIT, I decided to 
just link the source into the Xlib directory and build those routines 
right into the Xlib archive.

When I changed to autofoo for fd.o, I couldn't directly access the Xau 
source code as it was separately compiled, and not available while 
building Xlib.  So, instead, I just used -lXau and had X applications use 
the shared Xau library.

If we want to use the Xau routines right in Xlib, we can use the xtrans 
hack which installs the .c files into the include directory and then have 
Xlib reference those files.  As those functions haven't changed in "a 
while", it might be OK.

-keith