Added externs declarations to header files to handle C++ compilation.

Cleaned up BACnet/IP API a little.

bacnet-stack/handlers.h

@@ -36,6 +36,10 @@ extern bool I_Am_Request;
 // flag to send a global Who-Is
 extern bool Who_Is_Request;
 
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
 void UnrecognizedServiceHandler(
   uint8_t *service_request,
   uint16_t service_len,
@@ -87,4 +91,8 @@ void AtomicReadFileAckHandler(
   BACNET_ADDRESS *src,
   BACNET_CONFIRMED_SERVICE_ACK_DATA *service_data);
 
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
 #endif