STM32H743 FreeRTOS+TCP issue with ZERO Copy

Libraries
51

I created PR #544 which adds the new function FreeRTOS_get_tx_base().

Would you be able to check it?

I tested it as follows:

{
    BaseType_t xLength;
    uint8_t * pucBase = FreeRTOS_get_tx_base( xSocket );
    uint8_t * pucHead = FreeRTOS_get_tx_head( xSocket, &( xLength ) );
    FreeRTOS_printf( ( "httpTest: TX base = %p head = %p diff %u\n",
                       ( void * ) pucBase,
                       ( void * ) pucHead,
                       ( unsigned ) ( pucHead - pucBase ) ) );
}

When called before the first FreeRTOS_send(), the functions will create the TX buffer.
It will return NULL in case there was not enough heap.