QMP: Asynchronous events infrastructure

Asynchronous events are generated with a call to
monitor_protocol_event().

This function builds the right data-type and emit the event
right away. The emitted data is always a JSON object and its
format is as follows:

{ "event": json-string,
  "timestamp": { "seconds": json-number, "microseconds": json-number },
  "data": json-value }

This design is based on ideas by Amit Shah <amit.shah@redhat.com>.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

monitor.h

@@ -13,6 +13,12 @@ extern Monitor *cur_mon;
 #define MONITOR_USE_READLINE  0x02
 #define MONITOR_USE_CONTROL   0x04
 
+/* QMP events */
+typedef enum MonitorEvent {
+    EVENT_MAX,
+} MonitorEvent;
+
+void monitor_protocol_event(MonitorEvent event, QObject *data);
 const char *monitor_cmdline_parse(const char *cmdline, int *flags);
 void monitor_init(CharDriverState *chr, int flags);