Use __attribute__((fallthrough)) rather than magic GCC comments.

GCC added an implicit-fallthrough warning a while back, where it
would complain if you had a nontrivial "case:" block that didn't end
with break, return, or something like that.  Clang recently added
the same thing.

GCC, however, would let you annotate a fall-through as intended by
any of various magic "/* fall through */" comments.  Clang, however,
only seems to like "__attribute__((fallthrough))".  Fortunately, GCC
accepts that too.

A previous commit in this branch defined a FALLTHROUGH macro to do
the right thing if GNUC is defined; here we replace all of our "fall
through" comments with uses of that macro.

This is an automated commit, made with the following perl one-liner:

  #!/usr/bin/perl -i -p
  s#/\* *falls? ?thr.*?\*/#FALLTHROUGH;#i;

1 files changed, 1 insertions, 1 deletions

diff --git a/src/core/or/circuitbuild.c b/src/core/or/circuitbuild.c
index 21369fb538..f3a5791d6c 100644
--- a/src/core/or/circuitbuild.c
+++ b/src/core/or/circuitbuild.c
@@ -2106,7 +2106,7 @@ choose_good_exit_server(origin_circuit_t *circ,
       /* For these three, we want to pick the exit like a middle hop,
        * since it should be random. */
       tor_assert_nonfatal(is_internal);
-      /* Falls through */
+      FALLTHROUGH;
     case CIRCUIT_PURPOSE_C_GENERAL:
       if (is_internal) /* pick it like a middle hop */
         return router_choose_random_node(NULL, options->ExcludeNodes, flags);