Replace nearly all XXX0vv comments with smarter ones

So, back long ago, XXX012 meant, "before Tor 0.1.2 is released, we
had better revisit this comment and fix it!"

But we have a huge pile of such comments accumulated for a large
number of released versions!  Not cool.

So, here's what I tried to do:

  * 0.2.9 and 0.2.8 are retained, since those are not yet released.

  * XXX+ or XXX++ or XXX++++ or whatever means, "This one looks
    quite important!"

  * The others, after one-by-one examination, are downgraded to
    plain old XXX.  Which doesn't mean they aren't a problem -- just
    that they cannot possibly be a release-blocking problem.

1 files changed, 5 insertions, 4 deletions

diff --git a/src/or/directory.c b/src/or/directory.c
index 67b54c003d..abac19db2f 100644
--- a/src/or/directory.c
+++ b/src/or/directory.c
@@ -494,8 +494,9 @@ MOCK_IMPL(void, directory_get_from_dirserver, (
        * sort of dir fetch we'll be doing, so it won't return a bridge
        * that can't answer our question.
        */
-      /* XXX024 Not all bridges handle conditional consensus downloading,
-       * so, for now, never assume the server supports that. -PP */
+      /* XXX+++++ Not all bridges handle conditional consensus downloading,
+       * so, for now, never assume the server supports that. -PP
+       * Is that assumption still so in 2016? -NM */
       const node_t *node = choose_random_dirguard(type);
       if (node && node->ri) {
         /* every bridge has a routerinfo. */
@@ -2247,7 +2248,7 @@ connection_dir_client_reached_eof(dir_connection_t *conn)
                        ds->nickname);
               /* XXXX use this information; be sure to upload next one
                * sooner. -NM */
-              /* XXXX023 On further thought, the task above implies that we're
+              /* XXXX++ On further thought, the task above implies that we're
                * basing our regenerate-descriptor time on when we uploaded the
                * last descriptor, not on the published time of the last
                * descriptor.  If those are different, that's a bad thing to
@@ -3031,7 +3032,7 @@ handle_get_status_vote(dir_connection_t *conn, const get_handler_args_t *args)
     ssize_t estimated_len = 0;
     smartlist_t *items = smartlist_new();
     smartlist_t *dir_items = smartlist_new();
-    int lifetime = 60; /* XXXX023 should actually use vote intervals. */
+    int lifetime = 60; /* XXXX?? should actually use vote intervals. */
     url += strlen("/tor/status-vote/");
     current = !strcmpstart(url, "current/");
     url = strchr(url, '/');