Enhancement work for NMS-5423

Enable the SNMP code to digest OCTET STRING values acting as proto-Counter64
objects as seen in the FCMGMT-MIB with the following comment:

-- There is one and only one statistics table for each
-- individual port. For all objects in statistics table, if the object is not
-- supported by the conn unit then the high order bit is set to 1 with all other
-- bits set to zero. The high order bit is reserved to indicate if the object
-- if supported or not. All objects start at a value of zero at hardware
-- initialization and continue incrementing till end of 63 bits and then
-- wrap to zero.