Functions for weakly connected components

[Peter Kovacs]

I suggest to have the following functions:

bool weaklyConnected (const Digraph &graph);
int countWeaklyConnectedComponents (const Digraph &graph);
int weaklyConnectedComponents (const Digraph &graph, NodeMap &compMap);

which would work the same way as connected(), countConnectedComponents() and connectedComponents() for the undirected version of the digraph.

These proposed functions could be implemented easily using the Undirector adaptor and the undirected connectivity tools.