Add common utilities for JavaHL new-style map iterations.

* subversion/bindings/javahl/native/Utility.hpp,
  subversion/bindings/javahl/native/Utility.cpp: New files.
  (JavaHL::Util::make_keyword_hash, JavaHL::Util::make_property_hash):
   New utility functions for iterating over a Java::Map.

* subversion/bindings/javahl/native/org_apache_subversion_javahl_util_SubstLib.cpp
  (KeywordHashBuilder, make_keywords_hash): Removed.
  (translate_stream_common): Use JavaHL::Util::make_keyword_hash instead.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1545925 13f79535-47bb-0310-9956-ffa450edef68