swig: fix gcc8 warnings for cast between incompatible function types

swig: fix gcc8 warnings for cast between incompatible function types

We got an error when building setools in meta-selinux:
setools/policyrep/qpol_wrap.c:1819:23:
error: cast between incompatible function types from 'PyObject * (*)(PyObject *)'
{aka 'struct _object * (*)(struct _object *)'} to 'PyObject * (*)(PyObject *, PyObject *)'
{aka 'struct _object * (*)(struct _object *, struct _object *)'} [-Werror=cast-function-type]
{(char *)"disown", (PyCFunction)SwigPyObject_disown, METH_NOARGS, (char *)"releases ownership of the pointer"},

This is a swig issue. See: https://github.com/swig/swig/issues/1259
Backport a patch from upstream to fix it.

Signed-off-by: Yi Zhao <yi.zhao@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>