Added MSV object API create/delete/cleanup. Added BIP6 API for Contiki. (#134)

Co-authored-by: Steve Karg <skarg@users.sourceforge.net>

src/bacnet/basic/object/msv.h

@@ -126,6 +126,16 @@ extern "C" {
         uint32_t object_instance,
         uint32_t state_index);
 
+    BACNET_STACK_EXPORT
+    bool Multistate_Value_Create(
+        uint32_t object_instance);
+    BACNET_STACK_EXPORT
+    bool Multistate_Value_Delete(
+        uint32_t object_instance);
+    BACNET_STACK_EXPORT
+    void Multistate_Value_Cleanup(
+        void);
+
     BACNET_STACK_EXPORT
     void Multistate_Value_Init(
         void);

src/bacnet/datalink/bip6.h

@@ -95,7 +95,12 @@ extern "C" {
         BACNET_IP6_ADDRESS *addr,
         uint8_t * mtu,
         uint16_t mtu_len);
-
+    BACNET_STACK_EXPORT
+    bool bip6_send_pdu_queue_empty(
+        void);
+    BACNET_STACK_EXPORT
+    void bip6_receive_callback(
+        void);
 
 #ifdef __cplusplus
 }