THRIFT-928. cpp: Processor-level event callbacks

- Add a TProcessorEventHandler callback interface.
- Add methods to TProcessor to hold an instance of the interface.
- Add code to the compiler to make the processor call callbacks at key points.
- Add an optional processor event handler to the test server.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@1005126 13f79535-47bb-0310-9956-ffa450edef68
3 files changed