Add static method lookup and invocation to JavaHL's jniwrapper.

* subversion/bindings/javahl/native/jniwrapper/jni_env.hpp
  (Java::Env::GetStaticMethodID,
   Java::Env::CallStatic*Method): New methods.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1603297 13f79535-47bb-0310-9956-ffa450edef68