Fix/router ipv6 test (#806)

* fix app router-ipv6: duplicate symbol
Makefile use Device_Object_Instance_Number from device-client.c (Device_Object_Instance_Number is not in bacnet.a from Makefile)

Cmake use Device_Object_Instance_Number from libbacnet-stac.a:device.c

This fix #778

* test ipv6

CMakeLists.txt

@@ -67,7 +67,7 @@ option(
 option(
   BACDL_BIP6
   "compile with ipv6 datalink support"
-  OFF)
+  ON)
 
 if(NOT (BACDL_ETHERNET OR
         BACDL_MSTP OR
@@ -945,11 +945,8 @@ if(BACNET_STACK_BUILD_APPS)
       router-ipv6
       PRIVATE ${PROJECT_NAME})
     target_compile_options(router-ipv6 PRIVATE
-      # These make this example not totally C90 compatible but it is ok.
-
-      -Wno-declaration-after-statement
-      -Wno-overlength-strings
-      -Wno-variadic-macros
+      # Unreachable code because we have endless loop.
+      $<$<C_COMPILER_ID:MSVC>:/wd4702>
     )
   endif()