phases: add set per phase in C phase computation To speed up the computation of draft(), secret(), divergent(), obsolete() and unstable() we need to have a fast way of getting the list of revisions that are in draft(), secret() or the union of both: not public(). This patch extends the work on phase computation in C and make the phase computation code also return a list of set for each non public phase. Using these sets we can quickly obtain all the revisions of a given phase. We do not return a set for the public phase as we expect it to be roughly the size of the repo. Also, it can be computed easily by substracting the entries in the non public phases from all the revs in the repo.