Increase semicolons in the header comment from 3 to 4 (crucial).
Add failing tests for p84.
Add two missing solutions to tests.
Add adjacent-edges.

Adjacent-edges returns a list of edges that are adjacent to a given
vertex.
Simplify the predicates to remove-if in next-f.

In the case of adding new edges to f, we can first call adjacent-edges
to get a list of just the edges adjacent to v, and then filter out those
whose terminus is in pst. In the case of removing edges from f, there is
no need to call contains-vertex, since it will always return
true (because by design, f is a list of edges from verticies in pst to
vertices not in pst).
Rename f -> cut-set and next-f -> next-cut-set.

F was the name given to the cut-set in the algorithm presented in the
Gabows / Meyers paper. Renaming it to the more descriptive cut-set in
preparation for re-using the function next-cut-set in the solution to
p84.
Solution for p84.