Fix svn_auth_cleanup_walk()'s SWIG-Python manifestation.

* subversion/bindings/swig/core.i
  Add typemap for svn_auth_cleanup_func_t/baton pair.

* subversion/bindings/swig/python/libsvn_swig_py/swigutil_py.h,
* subversion/bindings/swig/python/libsvn_swig_py/swigutil_py.c
  (svn_swig_py_auth_cleanup_func): New function.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1465089 13f79535-47bb-0310-9956-ffa450edef68