Update JavaHL to use the revised svn_client_merge5 and svn_client_merge_peg5 APIs.

[in subversion/bindings/javahl/src/org/apache/subversion/javahl]
* ISVNClient.java, SVNClient.java (ISVNClient.merge): Add two new
   overloads that match the new svn_client functions.
   In the peg-merge case, allow passing a null revision range.

[in subversion/bindings/javahl/native]
* SVNClient.h, SVNClient.cpp (SVNClient::merge): Update the native implementation
   to accept the new svn_client parameters, and also accept a null revision range.
* org_apache_subversion_javahl_SVNClient.cpp: Update JNI native wrappers.


[in subversion/bindings/javahl/tests/org/apache/subversion/javahl]
* BasicTests.java (BasicTests.testMergeUsingHistoryImpliedRange):
   New test case, verifies that null merge range works as expected.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1463271 13f79535-47bb-0310-9956-ffa450edef68