[DOC]: Fix API Manual inconsistencies.

• The API Manual describes 0 as an allowed value for ulAnswerTimeout and ulOmbOpenTime.
• Missing usPort setting in code example:

/* Extended Modbus/TCP Configuration - structure*/
{typedef struct OMB_IF_CONFIG_EXT_Ttag
uint32_t ulProcessWatchdog; /* process data watchdog */
uint32_t ulInactiveTimeout; /* Server connection inactivity timeout */
uint16_t usMaxRegisterNumber; /* Maximum addressable registers */
uint16_t usMaxCoilsNumber; /* Maximum addressable coils */
uint16_t usFragmentationTimeout; /* Fragmentation Timeout */
uint16_t usReserved; /* Reserved, set to 0 */
} OMB_IF_CONFIG_EXT_T;

• update references to external documents