Added reject response to unknown reserved network layer message types. (#690)

src/bacnet/bacenum.h

@@ -1714,6 +1714,8 @@ typedef enum {
     NETWORK_MESSAGE_WHAT_IS_NETWORK_NUMBER = 18,
     NETWORK_MESSAGE_NETWORK_NUMBER_IS = 19,
     /* X'14' to X'7F': Reserved for use by ASHRAE, */
+    NETWORK_MESSAGE_ASHRAE_RESERVED_MIN = 20,
+    NETWORK_MESSAGE_ASHRAE_RESERVED_MAX = 127,
     /* X'80' to X'FF': Available for vendor proprietary messages */
     NETWORK_MESSAGE_INVALID = 0x100
 } BACNET_NETWORK_MESSAGE_TYPE;