[analyze-project-deps.py] Add the ability to list all cycles.

This analyzes the dependency graph and computes all minimal
cycles.  Equivalent cycles that differ only by rotation are
excluded, as are cycles that are "super-cycles" of other
smaller cycles.  For example, if we discover the cycle
A -> C -> A, and then later A -> B -> C -> D -> A, this latter
cycle is not considered.  Thus, it is possible that after
eliminating some cycles, new ones will appear.  However,
this is the only way to make the algorithm terminate in
a reasonable amount of time.

llvm-svn: 298324