cpp: Fix "make check" by defining a comparator for "Empty"

The TCompactProtocol revision added a "set<Empty>" in DebugProtoTest.
C++ needs a comparator in order to link this.


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@743111 13f79535-47bb-0310-9956-ffa450edef68
2 files changed