(perl #128438) build ppport.h instead of using a dummy file

(perl #128438) build ppport.h instead of using a dummy file

The changes to parallelize win32 perl builds with dmake and gmake
assumed that ppport.h only provided macros and functions that are
already provided by the latest perl.

This turns out not to be the case, preventing the building of
a new Scalar-List-Utils with dmake and gmake.

I only briefly considered changing Scalar-List-Utils - the difference
in build systems is what lead to the failure, so properly build ppport.h
so that all Win32 builds have a full ppport.h just as POSIXish builds
do.