Add native wrapper boilerplate for JavaHL's AuthnCallback
and UserPasswordCallback.

[in subversion/bindings/javahl]
* native/AuthnCallback.hpp, native/AuthnCallback.cpp: New.

* native/jniwrapper/jni_object.hpp
  (Java::ClassCache): Declare class objects for AuthnCallback & Co.
* native/jniwrapper/jni_class_cache.cpp
  (Java::ClassCache): Call initializers for AuthnCallback & Co.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1599255 13f79535-47bb-0310-9956-ffa450edef68