Implement Python bindings for dump stream parser.

* subversion/bindings/swig/include/svn_types.swg
  (): Fix a typo in svn_repos_parser_fns2_t type name, add
  svn_repos_parser_fns2_t type to the argout typemap.

* subversion/bindings/swig/python/libsvn_swig_py/swigutil_py.c
  (item_baton): Add pool; needed for certain methods in dump
  stream parser that do not take pool argument.
  (make_baton): Increment refcount on `editor'; remove incorrect
  the comment stating the current usage is safe. Save pool pointer.
  (close_baton): Decrement refcount on `editor'.
  (svn_swig_py_make_parse_fns3): New function; creates vtable/baton
  to be used in a later call to repos.parse_dumpstream3()

* subversion/bindings/swig/python/libsvn_swig_py/swigutil_py.h:
  (svn_swig_py_make_parse_fns3): New function.

* subversion/bindings/swig/python/svn/core.py
  (Stream.close): Guard against double-close.

* subversion/bindings/swig/python/svn/repos.py
  (ParseFns3): New class; vtable for dump stream parser.

* subversion/bindings/swig/python/tests/repository.py
  (test_parse_fns3): Test for dump stream parser bindings.
  (test_unnamed_editor): Test for make_baton/close_baton fix.

* subversion/bindings/swig/svn_repos.i
  (svn_swig_py_make_parse_fns3): Wrap it.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1642813 13f79535-47bb-0310-9956-ffa450edef68