Change the callback function to use void**.

NOTE: This change breaks backwards-compatibility by default.
If you have old callback functions, you can define PB_OLD_CALLBACK_STYLE
to retain the old behaviour.

If you want to convert your old callbacks to new signature, you need
to do the following:

1) Change decode callback argument to   void **arg
      and encode callback argument to   void * const *arg.

2) Change any reference to arg into *arg.

The rationale for making the new behaviour the default is that it
simplifies the common case of "allocate some memory in decode callback".

Update issue 69
Status: FixedInGit

tests/decode_unittests.c

@@ -19,11 +19,11 @@ bool stream_callback(pb_istream_t *stream, uint8_t *buf, size_t count)
 }
 
 /* Verifies that the stream passed to callback matches the byte array pointed to by arg. */
-bool callback_check(pb_istream_t *stream, const pb_field_t *field, void *arg)
+bool callback_check(pb_istream_t *stream, const pb_field_t *field, void **arg)
 {
     int i;
     uint8_t byte;
-    pb_bytes_array_t *ref = (pb_bytes_array_t*) arg;
+    pb_bytes_array_t *ref = (pb_bytes_array_t*) *arg;
     
     for (i = 0; i < ref->size; i++)
     {