Fix coreHTTP demo compile warning (FreeRTOS#1219)

Co-authored-by: Rahul Kar <118818625+kar-rahul-aws@users.noreply.github.com>

Author: chinglee-iot

FreeRTOS-Plus/Demo/coreHTTP_Windows_Simulator/HTTP_Mutual_Auth/DemoTasks/MutualAuthHTTPExample.c

@@ -200,6 +200,10 @@ static BaseType_t prvSendHttpRequest( const TransportInterface_t * pxTransportIn
 
 /*-----------------------------------------------------------*/
 
+extern BaseType_t xPlatformIsNetworkUp( void );
+
+/*-----------------------------------------------------------*/
+
 /*
  * @brief Create the task that demonstrates the HTTP API Demo over a
  * mutually-authenticated network connection with an HTTP server.

FreeRTOS-Plus/Demo/coreHTTP_Windows_Simulator/HTTP_Plaintext/DemoTasks/PlainTextHTTPExample.c

@@ -260,6 +260,10 @@ static BaseType_t prvSendHttpRequest( const TransportInterface_t * pxTransportIn
 
 /*-----------------------------------------------------------*/
 
+extern BaseType_t xPlatformIsNetworkUp( void );
+
+/*-----------------------------------------------------------*/
+
 /*
  * @brief Create the task that demonstrates the HTTP API Demo over a
  * mutually-authenticated network connection with an HTTP server.

FreeRTOS-Plus/Demo/coreHTTP_Windows_Simulator/HTTP_S3_Download_Multithreaded/DemoTasks/S3DownloadMultithreadedHTTPExample.c

@@ -429,6 +429,10 @@ static BaseType_t prvDownloadLoop( void );
 
 /*-----------------------------------------------------------*/
 
+extern BaseType_t xPlatformIsNetworkUp( void );
+
+/*-----------------------------------------------------------*/
+
 /*
  * @brief Create task to demonstrate the HTTP API over a server-authenticated
  * network connection with a server.

FreeRTOS-Plus/Demo/coreHTTP_Windows_Simulator/HTTP_S3_Upload/DemoTasks/S3UploadHTTPExample.c

@@ -295,6 +295,10 @@ static BaseType_t prvVerifyS3ObjectFileSize( const TransportInterface_t * pxTran
 
 /*-----------------------------------------------------------*/
 
+extern BaseType_t xPlatformIsNetworkUp( void );
+
+/*-----------------------------------------------------------*/
+
 /*
  * @brief Create the task that demonstrates the HTTP API Demo over a
  * server-authenticated network connection with an HTTP server.