monitor: rename EVENT_* to QEVENT_* to avoid conflict on mingw32

Partially fixes mingw32 build.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/monitor.h b/monitor.h
index 851fd33..38cc223 100644
--- a/monitor.h
+++ b/monitor.h
@@ -15,12 +15,12 @@
 
 /* QMP events */
 typedef enum MonitorEvent {
-    EVENT_DEBUG,
-    EVENT_SHUTDOWN,
-    EVENT_RESET,
-    EVENT_POWERDOWN,
-    EVENT_STOP,
-    EVENT_MAX,
+    QEVENT_DEBUG,
+    QEVENT_SHUTDOWN,
+    QEVENT_RESET,
+    QEVENT_POWERDOWN,
+    QEVENT_STOP,
+    QEVENT_MAX,
 } MonitorEvent;
 
 void monitor_protocol_event(MonitorEvent event, QObject *data);