[sldev] Visual Studio build change

[Soft]

If you're using Visual Studio for your builds, you now need to add
cygwin to your Visual Studio path. It no longer relies on a hard-coded
cygwin location.

In VS2003 this is at tools->options->projects->vc++ directories, "show
directories for: executable files." Here, add c:\cygwin\bin or local
equivalent. I suggest adding it to the very bottom of the list so
cygwin binaries don't supercede Windows commands with the same name.