Cygwin port of Guile 2.2

[Mike Gran]

Hello All,

I push a branch that mostly makes Guile 2.2 work on Cygwin.

In the end, I had a few issues.

Cygwin's uselocale is broken and can segrault.  I fell back
to the standard nl-langinfo.  I understand the issue and may
push a patch upstream to Cygwin sometime.

Also Cygwin's langinfo is incomplete with regards to LC
MONETARY.  This also is fixable upstream in Cygwin.

Cygwin requires stability on both ends of a pipe being used
for inter-thread communication.  If one tries to read from a
pipe that is closing on the other end, Cygwin may fault.  I
worked around this by replacing pipes with a
producer/consumer pattern of semaphores and mutex-protected
variables.  A dirty workaround.

Lastly, Cygwin's fork just doesn't play well with Guile's
new GC and threading model.  Despite a copy of days in the
guts of it all, I don't understand the specifics of the
issue.  So, in the branch, I disabled forking altogether,
and by extension, popen and friends.

While I couldn't get fork to work, the other threading
primitives seem fine.

The branch is wip-cygwin-guile-2.2.

Thanks,

Mike Gran