python: adjust module initalization for Python3

python: adjust module initalization for Python3

In Python3, PyTypeObject looks slightly different, and also module
initialization is different. Instead of Py_InitModule, PyModule_Create
should be called on already defined PyModuleDef structure. And then
initialization function should return that module.

Additionally initialization function should be named PyInit_<name>,
instead of init<name>.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>