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, 2 insertions, 2 deletions

diff --git a/src/core/or/circuitlist.c b/src/core/or/circuitlist.c
index 145004c71d..be5ac3b7f6 100644
--- a/src/core/or/circuitlist.c
+++ b/src/core/or/circuitlist.c
@@ -787,7 +787,7 @@ circuit_purpose_to_controller_hs_state_string(uint8_t purpose)
              "Unrecognized circuit purpose: %d",
              (int)purpose);
       tor_fragile_assert();
-      /* fall through */
+      FALLTHROUGH;
 
     case CIRCUIT_PURPOSE_OR:
     case CIRCUIT_PURPOSE_C_GENERAL:
@@ -2738,7 +2738,7 @@ assert_cpath_layer_ok(const crypt_path_t *cp)
     {
     case CPATH_STATE_OPEN:
       relay_crypto_assert_ok(&cp->crypto);
-      /* fall through */
+      FALLTHROUGH;
     case CPATH_STATE_CLOSED:
       /*XXXX Assert that there's no handshake_state either. */
       tor_assert(!cp->rend_dh_handshake_state);