Fix (most) compilation warnings in Intel C++ Compiler (#38)

* Use BACNET_OBJECT_TYPE for all object type variables.

* Fix ICC "mixing enumerated type" warnings for assignments and parameters.

* Network Port: Use enums for state structs and remove erroneous bounds checks copy-pasted from IP_Subnet_Prefix setter.

* Fix ICC "unreachable statement" warnings.

* Fix ICC "unused variable" warnings when printing is disabled.

* Fix ICC "mixing enumerated type" warnings for struct initializers { 0 } by ensuring the first member is an integer type.

* Send_GetEvent_Global: Return 0 (invalid TSM invoke ID) instead of -1 = 255 (technically valid invoke ID) on failure.

* Fix ICC "pointless comparison" warnings.

* Fix wrong import in objects.c (memset being used).

* Fix signedness warnings and inconsistencies. Include -1 = 255 check in cov_address_get().

* Add some guards for BACAPP_LIGHTING_COMMAND to avoid errors/warnings.

* RPM test fixes

* Address requested changes. (#38)

src/bacnet/basic/object/gateway/gw_device.c

@@ -112,8 +112,8 @@ uint16_t iCurrent_Device_Idx = 0;
  * @param Object_Instance [in] Set the new Device to this instance number.
  * @param sObject_Name [in] Use this Object Name for the Device.
  * @param sDescription [in] Set this Description for the Device.
- * @return The index of this instance in the Devices[] array,
- *         or -1 if there isn't enough room to add this Device.
+ * @return The index of this instance in the Devices[] array, or UINT16_MAX if
+ *         there isn't enough room to add this Device.
  */
 uint16_t Add_Routed_Device(uint32_t Object_Instance,
     BACNET_CHARACTER_STRING *sObject_Name,
@@ -141,7 +141,7 @@ uint16_t Add_Routed_Device(uint32_t Object_Instance,
         pDev->Database_Revision = 0; /* Reset/Initialize now */
         return i;
     } else {
-        return -1;
+        return UINT16_MAX;
     }
 }