Fix value truncation checks in JavaHL.

* subversion/bindings/javahl/native/CreateJ.cpp
  (CreateJ::ClientNotifyInformation): Check for signed overflow.
* subversion/bindings/javahl/native/JNIUtil.cpp
  (JNIUtil::handleSVNError): Likewise.

Found by: philipm


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1519913 13f79535-47bb-0310-9956-ffa450edef68