Windows will no longer be supported by ASDF, or ASDF, Windows, Cygwin -- oh, my!

[Robert Goldman]

I have a fix for test-sysdef-asdf that I have checked in in 3.1.6.17.

Briefly, the test previously used a call out with RUN-PROGRAM to find
the build script's notion of what the set of files in ASDF is, and then
compare that with what's in asdf.asd.  I couldn't get that to run for me.

I replaced the call out using RUN-PROGRAM with some lisp code that does
the same task.

Please LMK if that works now.