QMP: Introduce RTC_CHANGE event

Emitted whenever the RTC time changes.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/vl.c b/vl.c
index 03a47a4..d8328c7 100644
--- a/vl.c
+++ b/vl.c
@@ -1492,6 +1492,15 @@
     return seconds - time(NULL);
 }
 
+void rtc_change_mon_event(struct tm *tm)
+{
+    QObject *data;
+
+    data = qobject_from_jsonf("{ 'offset': %d }", qemu_timedate_diff(tm));
+    monitor_protocol_event(QEVENT_RTC_CHANGE, data);
+    qobject_decref(data);
+}
+
 static void configure_rtc_date_offset(const char *startdate, int legacy)
 {
     time_t rtc_start_date;