Ports Java Ticl refactoring to C++. This CL also fixes a couple minor nits
discovered in the Ticls while doing the porting.

Original change description:

Refactors the Java Ticl to enable the new Android design:

  1. Makes ProtocolHandler a less-active class. Messages are now received by
     InvalidationClientCore, which makes a call against ProtocolHandler to
     parse the message and receives back a parsed-messaged object in response.

  2. ProtocolHandler batching functionality is moved into a nested subclass to
     be more-easily persisted.

  3. InvalidationClientImpl is split into two classes. InvalidationClientCore
     and InvalidationClientImpl. InvalidationClientCore is the bulk of the old
     InvalidationClientImpl, containing all of the core logic involved in the
     Ticl, but no concurrency control. InvalidationClientImpl contains an
     InvalidationClientCore and adds the concurrency control. Specifically, the
     model is that ICI can make assertions about which thread it is executing on,
     and it can use schedulers to schedule events in the future or to enqueue something
     onto the listener thread, but it never does a schedule(NO_DELAY) on the internal
     thread. It is the responsibility of the caller to ensure that such calls are made
     on the internal thread.

This CL has a large number of lines changed because of the
InvalidationClientImpl / InvalidationClientCore split; it is not actually that
big a change in terms of line count.



git-svn-id: http://google-cache-invalidation-api.googlecode.com/svn/trunk@253 1cc9d426-c294-39be-ba72-c0199ca0f247