remove 'from datetime cimport *' line from cpython/__init__.pxd as it refers to a separate module, not the core C-API

--HG--
extra : rebase_source : bafa0a661abe97868fe254b3ce2b5e63b8654990

--HG--
extra : rebase_source : 6494c60e7f79a9cc85fe72a7adf325557f6de2be

This reverts commit 12d7dbb3.

Order cdef classes by inheritance before generating the code.

Hide Cython utility classes (like memoryview) from Python level module scope.

Do not generate tables for completely empty slot suites.

Fixes for absolute_import and inop test failures on Windows.

use pre-instantiated identifier string when looking up or setting the vtable of exported/imported extension types

handle some more cases where the error status is known to be used and clean up 'unraisable exception' code