Replace backslashes by forward slashes in MSVC build code

This makes it possible to run some stages of these build scripts on
non-Windows systems.  That way, we can more easily test whether file
moves or makefile changes might break the MSVC build.

Peter Eisentraut and Michael Paquier

Author: petere

src/tools/msvc/MSBuildProject.pm

@@ -127,7 +127,7 @@ EOF
 	foreach my $fileNameWithPath (sort keys %{ $self->{files} })
 	{
 		confess "Bad format filename '$fileNameWithPath'\n"
-		  unless ($fileNameWithPath =~ /^(.*)\\([^\\]+)\.(c|cpp|y|l|rc)$/);
+		  unless ($fileNameWithPath =~ m!^(.*)/([^/]+)\.(c|cpp|y|l|rc)$!);
 		my $dir      = $1;
 		my $fileName = $2;
 		if ($fileNameWithPath =~ /\.y$/ or $fileNameWithPath =~ /\.l$/)