Slot conflict due to cython and python 3.4

I just enabled `PYTHON_TARGETS="… python3_4"` on my system. As a consequence, I got a slot conflict: some packages required `dev-python/cython[python_targets_python3_4]` which could only be satisfied by the ebuilds for `cython-0.20`, while sage on the other hand required `cython-0.19`. So I imported the `cython-0.19.2` ebuild from the main portage tree, added python 3.4 support, and emerged that. Seems to work so far.