made _version2int compatible with development version of Cython
made _version2int compatible with development version of Cython

zasdfgbnm/qutip,qutip/qutip,qutip/qutip,anubhavvardhan/qutip,anubhavvardhan/qutip,zasdfgbnm/qutip,cgranade/qutip,cgranade/qutip