Add support for an explicit RTC change event

This introduces a new event type

   VIR_DOMAIN_EVENT_ID_RTC_CHANGE

This event includes the new UTC offset measured in seconds.
Thus there is a new callback definition for this event type

 typedef void (*virConnectDomainEventRTCChangeCallback)(virConnectPtr conn,
                                                        virDomainPtr dom,
                                                        long long utcoffset,
                                                        void *opaque);

If the guest XML configuration for the <clock> is set to
offset='variable', then the XML will automatically be
updated with the new UTC offset value. This ensures that
during migration/save/restore the new offset is preserved.

* daemon/remote.c: Dispatch RTC change events to client
* examples/domain-events/events-c/event-test.c: Watch for
  RTC change events
* include/libvirt/libvirt.h.in: Define new RTC change event ID
  and callback signature
* src/conf/domain_event.c, src/conf/domain_event.h,
  src/libvirt_private.syms: Extend API to handle RTC change events
* src/qemu/qemu_driver.c: Connect to the QEMU monitor event
  for RTC changes and emit a libvirt RTC change event
* src/remote/remote_driver.c: Receive and dispatch RTC change
  events to application
* src/remote/remote_protocol.x: Wire protocol definition for
  RTC change events
* src/qemu/qemu_monitor.c, src/qemu/qemu_monitor.h,
  src/qemu/qemu_monitor_json.c: Watch for RTC_CHANGE event
  from QEMU monitor

daemon/remote.c

@@ -157,9 +157,40 @@ static int remoteRelayDomainEventReboot(virConnectPtr conn ATTRIBUTE_UNUSED,
 }
 
 
+static int remoteRelayDomainEventRTCChange(virConnectPtr conn ATTRIBUTE_UNUSED,
+                                           virDomainPtr dom,
+                                           long long offset,
+                                           void *opaque)
+{
+    struct qemud_client *client = opaque;
+    remote_domain_event_rtc_change_msg data;
+
+    if (!client)
+        return -1;
+
+    REMOTE_DEBUG("Relaying domain rtc change event %s %d %lld", dom->name, dom->id, offset);
+
+    virMutexLock(&client->lock);
+
+    /* build return data */
+    memset(&data, 0, sizeof data);
+    make_nonnull_domain (&data.dom, dom);
+    data.offset = offset;
+
+    remoteDispatchDomainEventSend (client,
+                                   REMOTE_PROC_DOMAIN_EVENT_RTC_CHANGE,
+                                   (xdrproc_t)xdr_remote_domain_event_rtc_change_msg, &data);
+
+    virMutexUnlock(&client->lock);
+
+    return 0;
+}
+
+
 static virConnectDomainEventGenericCallback domainEventCallbacks[] = {
     VIR_DOMAIN_EVENT_CALLBACK(remoteRelayDomainEventLifecycle),
     VIR_DOMAIN_EVENT_CALLBACK(remoteRelayDomainEventReboot),
+    VIR_DOMAIN_EVENT_CALLBACK(remoteRelayDomainEventRTCChange),
 };
 
 verify(ARRAY_CARDINALITY(domainEventCallbacks) == VIR_DOMAIN_EVENT_ID_LAST);

daemon/remote_dispatch_table.h

@@ -852,3 +852,8 @@
     .args_filter = (xdrproc_t) xdr_void,
     .ret_filter = (xdrproc_t) xdr_void,
 },
+{   /* Async event DomainEventRtcChange => 170 */
+    .fn = NULL,
+    .args_filter = (xdrproc_t) xdr_void,
+    .ret_filter = (xdrproc_t) xdr_void,
+},