THRIFT-752. java: Use a faster Stack implementation in TCompactProtocol

THRIFT-752. java: Use a faster Stack implementation in TCompactProtocol

This patch adds ShortStack, an internal implementation of Stack that works directly on primitive short objects, and makes TCompactProtocol use this. A brief performance test shows that this makes serialization about 8% faster and deserialization about 15% faster, though the actual gain you see will be dependent on the nature of your structs - the more levels, the more gain.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@930593 13f79535-47bb-0310-9956-ffa450edef68