update msvc libffi to 3.3
We are vendoring an old copy of libffi in rpython/translator/c/src/libffi_msvc. It does not contain the fix for https://bugs.python.org/issue34603 and maybe other fixes. In https://bugs.python.org/issue35947 they removed the custom msvc libffi in favor of using the upstream one (for python 3.8), the PR is https://github.com/python/cpython/pull/11797
We should do the same. While CPython ships a libffi-7.dll, we could consider building it as a static library instead.
@nulano any thoughts?
xref issue #3366