Linux: Added commands to show threads and devices

The list_tasks and list_devices commands will show
lists of running px4 threads and created virtual device nodes.

The list_builtins command was removes and the list of commands
will be shown if return is pressed.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/drivers/device/vdev.cpp

@@ -454,5 +454,16 @@ VDev *VDev::getDev(const char *path)
 	return NULL;
 }
 
+void VDev::showDevices()
+{
+	int i=0;
+	printf("Devices:\n");
+	for (; i<PX4_MAX_DEV; ++i) {
+		if (devmap[i]) {
+			printf("   %s\n", devmap[i]->name);
+		}
+	}
+}
+
 } // namespace device