sd-device: add sd_device_monitor_get_event_source()

src/libsystemd/libsystemd.sym

@@ -659,6 +659,7 @@ global:
         sd_device_monitor_attach_event;
         sd_device_monitor_detach_event;
         sd_device_monitor_get_event;
+        sd_device_monitor_get_event_source;
         sd_device_monitor_start;
         sd_device_monitor_stop;
 

src/libsystemd/sd-device/device-monitor.c

@@ -272,6 +272,12 @@ _public_ sd_event *sd_device_monitor_get_event(sd_device_monitor *m) {
         return m->event;
 }
 
+_public_ sd_event_source *sd_device_monitor_get_event_source(sd_device_monitor *m) {
+        assert_return(m, NULL);
+
+        return m->event_source;
+}
+
 int device_monitor_enable_receiving(sd_device_monitor *m) {
         int r;