Finds all the critical links of a bidirected graph. We define an (bidirected) link as a pair of (oppositely directed) edges between two nodes. A critical link is one that, when removed, would make the graph more disconnected.
The result is returned as a list of links, where each link is a hyphenated pair of e/3 edge structures like e(I,J,Dij) - e(J,I,Dji).