Running a bdist_wininst installer, built with Python 2.3, installing

Running a bdist_wininst installer, built with Python 2.3, installing
for Python 2.4 caused a segfault when post_install_script was used.

The reason was that the file handle passed to PyRun_SimpleFile() was
created with MSVCRT.DLL, but Python 2.4 uses MSVCR71.DLL.

So, I replaced PyRun_SimpleFile() with PyRun_SimpleString().  The
segfault is gone, but the output of the postinstall script doesn't
show up, because still freopen() from MSVCRT is used.

(I would be very gratefull if someone proofreads the patch, at least).