TODO in unweighted shortest path implementations (BFS)?

@Gabor Do you recall why this is marked as TODO? I don’t see what’s wrong. There are several instances of the same and I am working with this code at the moment.

Because it assumes that igraph_Free() is the same as free().

igraph_Free() is a macro, so you cannot take its address, but we should also define igraph_Free() as a function, in addition to the macro, and then we could use it here as well.

We already have the function igraph_free(). I’ll change it to that.