Move to a zpkg-based setup:
- Switch to ZODB 3.5.0a7.
- References to headers now involve the package names.
- The setup.py in the checkout can only be used for "in-place" builds
(setup.py build_ext -i); you can't do out-of-place builds or
installations directly from a checkout (use a distribution package
- If you add C code to a package, make sure to update/create the
SETUP.cfg for that package, and make sure that package is listed in
setup.py at the top. (I expect we'll remove that last step before