[MLton] MLton on Cygwin

[Stephen Weeks]

I've made some progress getting MLton working on Cygwin again.

I did see the errors that Tom and Neophytos sent, and I get exactly
the same error as Neophytos when running MLton 20041109 on Cygwin
1.5.18-1.

I decided to start from scratch and try to get the new (svn) version
of MLton working on the new Cygwin rather than try to fix the old
MLton.  I'm getting closer to having something working on that front.
As I mentioned last month, there is some problem connected with our
use of Virtual{Alloc,Free} for obtaining memory, since if I run any
code compiled by the svn MLton on Cygwin, I get one of our error
messages at the first GC:

  VirtualFree release failed

However, I am able to get all of our regressions to pass on Cygwin,
provided that I run them with @MLton use-mmap --.

I'll investigate this further.  We might even adopt use-mmap as the
default behavior, depending on what I discover.  If anyone else on the
list has ideas about what might have changed in Cygwin that would
affect our use of Virtual{Alloc,Free}, please speak up.