Merge zlib warning fixes by rurban

https://github.com/madler/zlib/compare/develop...rurban:FALLTHROUGH?d=1.patch

common/zlib/infback.c

@@ -477,6 +477,7 @@ void FAR *out_desc;
             }
             Tracev((stderr, "inflate:       codes ok\n"));
             state->mode = LEN;
+            /* FALLTHROUGH */
 
         case LEN:
             /* use inflate_fast() if we have enough input and output */