Remove the use of some more deprecated APIs from JavaHL.

[in subversion/bindings/javahl]
* src/org/apache/subversion/javahl/SVNUtil.java
  (SVNUtil.DiffOptions): Add an option to set the diff context size.
* src/org/apache/subversion/javahl/util/DiffLib.java
  (DiffLib.fileDiff): Propagate the context size to nativeFileDiff.
  (DiffLib.nativeFileDiff): Accept a new context size parameter.

* native/org_apache_subversion_javahl_util_DiffLib.cpp
  (Java_org_apache_subversion_javahl_util_DiffLib_natveFileDiff):
   Update the prototype, and use svn_diff_file_output_unified4 with
   the context size instead of svn_diff_file_output_unified3.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1603354 13f79535-47bb-0310-9956-ffa450edef68