Add support for 64-bit _ctypes with MSVC.
Add support for 64-bit _ctypes with MSVC.

Tested-by: John R. Cary <42f8ad7a08fc008de6caead15912549a4a0ad947@txcorp.com>

adrianbroher/python-cmake-buildsystem,msmolens/python-cmake-buildsystem,davidsansome/python-cmake-buildsystem,chuckatkins/python-cmake-buildsystem,thewtex/python-cmake-buildsystem,python-cmake-buildsystem/python-cmake-buildsystem,thewtex/python-cmake-buildsystem,jcfr/python-cmake-buildsystem