Add multi-device support for BACnet gateway routing (#1279)

* Expanded Object_List to Object_List[MAX_NUM_DEVICES] array to support per-device objects for virtual remote devices
* Added multi-device iteration for COV handler, device timer, and intrinsic reporting
* Added apps/gateway2 demo application
* When MAX_NUM_DEVICES == 1, behavior is identical to the original implementation
* Conditional compilation with macros ensures no impact on non-gateway applications

---------

Signed-off-by: Hyeongjun Kim <hjun1.kim@samsung.com>
Co-authored-by: haemeok-kang <haemeok.kang@samsung.com>

apps/gateway2/gateway.h

@@ -0,0 +1,42 @@
+/**
+ * @file
+ * @brief Header for example gateway (ie, BACnet Router and Devices)
+ * using the BACnet Stack.
+ * @author Tom Brennan <tbrennan3@users.sourceforge.net>
+ * @date 2010
+ * @copyright SPDX-License-Identifier: MIT
+ */
+#ifndef BACNET_GATEWAY_H_
+#define BACNET_GATEWAY_H_
+
+#include "bacnet/config.h"
+
+/** @defgroup GatewayDemo Demo of a BACnet virtual gateway (multiple Device).
+ * @ingroup Demos
+ * This is a basic demonstration of a BACnet Router with child devices (ie,
+ * gateway) appearing on a virtual BACnet network behind the Router.
+ * This is an extension of the ServerDemo project.
+ */
+
+/* Device configuration definitions. */
+#define FIRST_DEVICE_NUMBER 260001
+#define VIRTUAL_DNET 2709 /* your choice of number here */
+#define DEV_NAME_BASE "Gateway Demo Device"
+#define DEV_DESCR_GATEWAY "Gateway Device and Router"
+#define DEV_DESCR_REMOTE "Routed Remote Device"
+#define VIRTUAL_DEVICE_COUNT 10
+#define VIRTUAL_DEVICE_INDEX_OFFSET 1
+
+#if VIRTUAL_DEVICE_COUNT >= MAX_NUM_DEVICES
+#ifdef _MSC_VER
+#pragma message( \
+    "VIRTUAL_DEVICE_COUNT >= MAX_NUM_DEVICES, adjusting to MAX_NUM_DEVICES-1")
+#else
+#warning \
+    "VIRTUAL_DEVICE_COUNT >= MAX_NUM_DEVICES, adjusting to MAX_NUM_DEVICES-1"
+#endif
+#undef VIRTUAL_DEVICE_COUNT
+#define VIRTUAL_DEVICE_COUNT (MAX_NUM_DEVICES - 1)
+#endif
+
+#endif