python: Add new helper functions for python to C integral conversion

python: Add new helper functions for python to C integral conversion

    int libvirt_intUnwrap(PyObject *obj, int *val);
    int libvirt_uintUnwrap(PyObject *obj, unsigned int *val);
    int libvirt_longUnwrap(PyObject *obj, long *val);
    int libvirt_ulongUnwrap(PyObject *obj, unsigned long *val);
    int libvirt_longlongUnwrap(PyObject *obj, long long *val);
    int libvirt_ulonglongUnwrap(PyObject *obj, unsigned long long *val);
    int libvirt_doubleUnwrap(PyObject *obj, double *val);
    int libvirt_boolUnwrap(PyObject *obj, bool *val);