swig-rb: Restore swig-rb to be compatible with Ruby 1.9 through 2.2.

* subversion/bindings/swig/include/svn_types.swg
  (%typemap(ret) svn_error_t *):
    Use `RARRAY_LEN` rather than `rb_array_len`.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1922418 13f79535-47bb-0310-9956-ffa450edef68

subversion/bindings/swig/include/svn_types.swg

@@ -546,7 +546,7 @@ svn_ ## TYPE ## _swig_rb_closed(VALUE self)
 %typemap(ret) svn_error_t *
 {
   if (TYPE(*svn_presult) == T_ARRAY) {
-    switch (rb_array_len(*svn_presult)) {
+    switch (RARRAY_LEN(*svn_presult)) {
       case 0:
         *svn_presult = Qnil;
         break;