Change code generator to give async event messages their own postfix

Change code generator to give async event messages their own postfix

The naming convention for structs used in the RPC layer is for
incoming requests to be called XXXX_args, and the associated
outgoing reply to be called XXXX_ret.  Asynchronously emitted
messages (eg events) are re-using the XXXX_ret naming scheme.
This patch changes that such that async messages are XXXX_msg,
and stops adding entries for them in the dispatch table, avoiding
the need for a dummy no-op implementation.

* qemud/remote.c: Remove dummy remoteDispatchDomainEvent, no
  longer required. Update to replace remote_domain_event_ret
  with xdr_remote_domain_event_msg
* qemud/remote_protocol.x: Rename remote_domain_event_ret to
  remote_domain_event_msg
* qemud/remote_generate_stubs.pl: Adding handling for new
  XXX_msg structs.
* src/remote_internal.c: Rename remote_domain_event_ret to
  remote_domain_event_msg
* qemud/remote_dispatch_prototypes.h, qemud/remote_dispatch_ret.h,
  qemud/remote_dispatch_table.h, qemud/remote_protocol.h,
  qemud/remote_protocol.c: auto-regenerate