NETINFO_ITEMs are not stored in a vector anymore, instead they are held in a unordered_map. Now, the net codes may be not consecutive. There is another way for assigning net codes (using a static int that holds a possible empty net code and a function that makes sure it is not used [getFreeNetCode()]).
Removed some unused fields (NETINFO_ITEM::m_NbNodes, m_NbLink, m_NbNoconn, m_Flag).