Bind get_client_string callback of svn_ra_callbacks2_t for Python.
* subversion/bindings/swig/python/libsvn_swig_py/swigutil_py.c
(ra_callbacks_get_client_string): Add callback wrapper.
(svn_swig_py_setup_ra_callbacks): Fill in get_client_string field with it.
* subversion/bindings/swig/python/svn/ra.py
(Callbacks.get_client_string): Add new attribute, initially None.
* subversion/bindings/swig/python/tests/ra.py
(test_namestring): Add test when URL starts with 'http'. Since we
can't yet run check-swig-py over http, this never runs. But gvn
tests this binding as of r636, so I know it works.
git-svn-id: http://svn.collab.net/repos/svn/trunk@28615 612f8ebc-c883-4be0-9ee0-a4e9ef946e3a