Add win32/*.[ch] to MANIFEST.in
Add win32/*.[ch] to MANIFEST.in

It's not clear that these files are still required on MinGW.
However while they are still used in setup.py, they should be
added to generated tarballs. Fixes #983.

pysam-developers/pysam,pysam-developers/pysam,pysam-developers/pysam,pysam-developers/pysam