Simplify classmethod() code in Py3 where "PyMethodDescr_Type" is directly available.
Simplify classmethod() code in Py3 where "PyMethodDescr_Type" is directly available.

scoder/cython,cython/cython,scoder/cython,da-woods/cython,cython/cython,da-woods/cython,da-woods/cython,cython/cython,cython/cython,scoder/cython,da-woods/cython,scoder/cython