forward vs backward slashes in msvc build code

I understand that on Windows, you can use forward slashes in path names
interchangeably with backward slashes (except possibly in the shell). I
have developed the attached patch to change the msvc build code to use
forward slashes consistently. Together with the other attached patch,
which is an unpolished hack, this allows me to run the build.pl script
on not-Windows. It won't actually build, but it will create all the
project files. That way, I can check whether some makefile hackery
would break the Windows build. Could someone verify this please?