[MLton-user] mingw or cygwin

[Stephen Weeks]

> Should also point out that a number of the functions in the OS
> structure are implemented in terms of Posix structure functions, so
> these are also unavailabe in MinGW.

I read through the basis code and the only such functions I could find
were:

  OS.FileSys.readLink
  OS.Process.terminate

Those were mistakenly not documented as missing at

  http://mlton.org/RunningOnMinGW

I have now fixed the documentation.  If there are other functions I
missed, please add them.