Fix the compatibility bug with Cython 0.2/python3 during installation.

Env: ubunutu 14.04
When installing gevent, Cython 0.21 add a title like 
/* generated by Cython 0.21 */
Cythonpp.py appends another */ after this line and that will mess the installation procedure.
/* generated by Cython 0.21 */ */