[AMQCPP-150] When performing tight unmarshalling of compressed long long values (e.g. int and short), cast the values to unsigned, so that the sign bit will not appear in the resulting long 

git-svn-id: https://svn.apache.org/repos/asf/activemq/activemq-cpp/trunk@589089 13f79535-47bb-0310-9956-ffa450edef68