On Fri, 20 Feb 2009, Francois Gouget wrote: [...]
Well, since Cygwin is a Unix platform after a fashion (iirc), I don't think you need to check with MSVC (with MinGW it would be different). So I think your patch is ok.
You should add a comment in the port.h file saying that this define is needed for Cygwin though (so the next one who stumbles on this suspicious define knows why it was put there).