Introduce a new-style JNI wrapper to the JavaHL native implementaiton.
The old-style, rather messy code will eventually be ported to this.

* build.conf
  (private-includes): Add JavaHL *.hpp and jniwrapper headers.
  (libsvnjavahl): Add jniwrapper sources.

* subversion/bindings/javahl/native/JNIUtil.cpp
  (g_jvm, JNI_OnLoad, JNI_OnUnload): Removed; replaced by equivalent
   functionality in jniwrapper.
  (JNIUtil::getEnv): Reimplement using jniwrapper's Java::Env class.

* subversion/bindings/javahl/native/jniwrapper: New directory.
* subversion/bindings/javahl/native/jniwrapper/jni_array.hpp,
  subversion/bindings/javahl/native/jniwrapper/jni_base.cpp,
  subversion/bindings/javahl/native/jniwrapper/jni_class_cache.cpp,
  subversion/bindings/javahl/native/jniwrapper/jni_env.hpp,
  subversion/bindings/javahl/native/jniwrapper/jni_exception.hpp,
  subversion/bindings/javahl/native/jniwrapper/jni_globalref.hpp,
  subversion/bindings/javahl/native/jniwrapper/jni_javahl_exception.hpp,
  subversion/bindings/javahl/native/jniwrapper/jni_list.cpp,
  subversion/bindings/javahl/native/jniwrapper/jni_list.hpp,
  subversion/bindings/javahl/native/jniwrapper/jni_object.hpp,
  subversion/bindings/javahl/native/jniwrapper/jni_stack.hpp: New files.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1539114 13f79535-47bb-0310-9956-ffa450edef68