Fix implicit fallthrough that trips -Werror

-Werror now trips on implicit fallthroughs. There is also at least one
that probably should not be, although it appears to be harmless.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

asm/listing.c

@@ -1,6 +1,6 @@
 /* ----------------------------------------------------------------------- *
  *
- *   Copyright 1996-2016 The NASM Authors - All Rights Reserved
+ *   Copyright 1996-2018 The NASM Authors - All Rights Reserved
  *   See the file AUTHORS included with the NASM distribution for
  *   the specific copyright holders.
  *
@@ -213,10 +213,11 @@ static void list_output(const struct out_data *data)
         if (size > 16) {
             snprintf(q, sizeof(q), "<zero %08"PRIX64">", size);
             list_out(offset, q);
+            break;
         } else {
             p = zero_buffer;
-            /* fall through */
         }
+        /* fall through */
     case OUT_RAWDATA:
     {
 	if (size == 0 && !listdata[0])

rdoff/rdflib.c

@@ -233,6 +233,7 @@ int main(int argc, char **argv)
             fprintf(stderr, "rdflib: required parameter missing\n");
             exit(1);
         }
+        break;
     case 't':
         fp = fopen(argv[2], "rb");
         if (!fp) {
@@ -317,6 +318,8 @@ int main(int argc, char **argv)
 
     case 'r':                  /* replace module */
         argc--;
+        /* fall through */
+
     case 'd':                  /* delete module */
         if (argc < 4) {
             fprintf(stderr, "rdflib: required parameter missing\n");