swig-py: Fix return value of svn_repos_fs_commit_txn().

* subversion/bindings/swig/svn_repos.i
  (typemap(argout) (const char **conflict_p, svn_repos_t *repos,
                    svn_revnum_t *new_rev)): New typemap.

Found by: cmpilato

Index: subversion/bindings/swig/svn_repos.i
===================================================================
--- subversion/bindings/swig/svn_repos.i	(revision 1880203)
+++ subversion/bindings/swig/svn_repos.i	(working copy)
@@ -109,6 +109,32 @@
 #endif
 
 /* -----------------------------------------------------------------------
+   Fix the return value for svn_repos_fs_commit_txn(). If the conflict
+   result is NULL, then %append_output() is passed Py_None, but that goofs
+   up because that is *also* the marker for "I haven't started assembling
+   a multi-valued return yet" which means the second return value
+   (new_rev) will not cause a 2-tuple to be manufactured.
+
+   The answer is to explicitly create a 2-tuple return value.
+
+   FIXME: Do the Perl and Ruby bindings need to do something similar?
+*/
+#ifdef SWIGPYTHON
+%typemap(argout) (const char **conflict_p, svn_repos_t *repos,
+                  svn_revnum_t *new_rev) {
+    /* this is always Py_None */
+    Py_DECREF($result);
+    /* build the result tuple */
+    $result = Py_BuildValue(
+%#if PY_VERSION_HEX >= 0x03000000
+                            "yi",
+%#else
+                            "zi",
+%#endif
+                            *$1, (long)*$3);
+}
+#endif
+/* -----------------------------------------------------------------------
    handle svn_repos_get_committed_info().
 */
 #ifdef SWIGRUBY