fix Py3.5 support: PyCFunction is now weak referencible itself, need to remove it from CyFunction
fix accidental argument name reuse in C macro
speed up method calls a little by inlining CPython's method_call() and avoiding duplicate args tuple packing

--HG--
extra : amend_source : 52480a79feadc93a60bdeee1837a31bf3539b327