This wires up the remote driver to handle the new events APIs.
The public API allows an application to request a callback filters
events to a specific domain object, and register multiple callbacks
for the same event type. On the wire there are two strategies for
this

 - Register multiple callbacks with the remote daemon, each
   with filtering as needed
 - Register only one callback per event type, with no filtering

Both approaches have potential inefficiency. In the first scheme,
the same event gets sent over the wire many times if multiple
callbacks are registered. With the second scheme, unneccessary
events get sent over the wire if a per-domain filter is set on
the client. The second scheme is far easier to implement though,
so this patch takes that approach.

* daemon/dispatch.h: Don't export remoteRelayDomainEvent since it
  is no longer needed for unregistering callbacks, instead the
  unique callback ID is used
* daemon/libvirtd.c, daemon/libvirtd.h: Track and unregister
  callbacks based on callback ID, instead of function pointer
* daemon/remote.c: Switch over to using virConnectDomainEventRegisterAny
  instead of legacy virConnectDomainEventRegister function. Refactor
  remoteDispatchDomainEventSend() to cope with arbitrary event types
* src/driver.h, src/driver.c: Move verify() call into source file
  instead of header, to avoid polluting the global namespace with
  the verify function name
* src/remote/remote_driver.c: Implement new APIs for event
  registration. Refactor processCallDispatchMessage() to cope
  with arbitrary incoming event types. Merge remoteDomainQueueEvent()
  into processCallDispatchMessage() to avoid duplication of code.
  Rename remoteDomainReadEvent() to remoteDomainReadEventLifecycle()
* src/remote/remote_protocol.x: Define wire format for the new
  virConnectDomainEventRegisterAny and virConnectDomainEventDeregisterAny
  functions