Pass SVN:Pool by reference otherwise a subpool gets created/destroyed
and the allocated memory becomes invalid.

* subversion/bindings/javahl/native/DiffOptions.h
* subversion/bindings/javahl/native/DiffOptions.cpp
  (DiffOptions::optionsArray): Pass pool by referance.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1456394 13f79535-47bb-0310-9956-ffa450edef68