Imported cython 0.19.2 ebuild from main portage tree.
Mark cython as supporting python 3.4.

That way one can enable the python_targets_python3_4 USE flag without
causing a slot conflict due to cython and sage.
Merge pull request #291 from gagern/cython-py34

Import cython 0.19.2 in the overlay and mark it compatible with python 3.4.