do not use cythonize() but Cython.Distutils in setup.py to avoid Cython compilation when not building the extensions

Conflicts:
	setup.py

clean up extension building in setup.py: clarify what's Py3.2-specific and use cythonize() instead of Cython.Distutils

undo incorrect coercion removal - passing through C types might be required due to low-level value conversions

Conflicts:
	CHANGES.rst