[pypy-dev] PyPy bugfix release 7.3.13

I am going to create a new release 7.3.13 to fix a problems in the conda feedstock. I improved the support for multiphase c-extension initialization immediately after the 7.3.12 release, and tried to merge pieces of it to the conda-forge feedstock but it has become too many patches to maintain. If there is anything you think I should add to the release, please file an issue and mark it with the 7.3.13 milestone. If the CFFI 1.16 release happens before I get too deep into the PyPy release process, I will try to update it. I had hoped to get most of hpy0.9 into this release, but there is still a lot to do. Matti