Add code into snmpit and snmpit_lib to support the implemented_by, the code check whether a VLAN is a link that implements a path consisting of two layer 1 links, if YES, move the vlanid to a special array, the CreateOneVlan is able to handle two stacks in that case. The ports in the special VLAN is in switch:card.port format when they are passed to snmpit_stack and the under driver.(snmpit_hp only.)