Added missing "fall through" comments to make GCC 7 happy.

src/nxt_http_parse.c

@@ -599,10 +599,13 @@ nxt_http_lookup_field_end(u_char *p, u_char *end)
     switch (end - p) {
     case 3:
         nxt_http_lookup_field_end_step
+        /* Fall through. */
     case 2:
         nxt_http_lookup_field_end_step
+        /* Fall through. */
     case 1:
         nxt_http_lookup_field_end_step
+        /* Fall through. */
     case 0:
         break;
     default:

src/nxt_murmur_hash.c

@@ -37,8 +37,10 @@ nxt_murmur_hash2(const void *data, size_t len)
     switch (len) {
     case 3:
         h ^= p[2] << 16;
+        /* Fall through. */
     case 2:
         h ^= p[1] << 8;
+        /* Fall through. */
     case 1:
         h ^= p[0];
         h *= m;