Revision of the patch from Andrew Kaylor <andrew.kaylor@intel.com> to prevent...

Revision of the patch from Andrew Kaylor <andrew.kaylor@intel.com> to prevent missing an event added in WaitForEventsInternal, narrowing the time in which we are not accepting new events.  Also, made everything that was protected private, since there really isn't any good reason why subclasses would have to muck with the listener internals.

llvm-svn: 167857