Add callback-based variants of the svn_ra_get_location_segments and
svn_ra_get_file_revs wrappers to JavaHL.

[in subversion/bindings/javahl/src/org/apache/subversion/javahl]
* callback/RemoteFileRevisionsCallback.java,
  callback/RemoteLocationSegmentsCallback.java: New interfaces.
* ISVNRemote.java (getLocationSegments, getFileRevisions): Added new
   overloads that drive their respective callbacks.
* remote/RemoteSession.java (getLocationSegments, getFileRevisions):
   Made the new overloads native, and implement the list-based ones in
   terms of the callback-based ones.

[in subversion/bindings/javahl/native]
* org_apache_subversion_javahl_remote_RemoteSession.cpp
  (Java_org_apache_subversion_javahl_remote_RemoteSession_getLocationSegments,
   Java_org_apache_subversion_javahl_remote_RemoteSession_getFileRevisions):
   Updated signatures and implementation of JNI wrappers.
* RemoteSession.h (getLocationSegments, getFileRevisions): Update prototypes.
* RemoteSession.cpp (getLocationSegments, getFileRevisions,
   LocationSegmentHandler, FileRevisionHandler): Update implementation.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1510909 13f79535-47bb-0310-9956-ffa450edef68