If node::Buffer::New() is used to wrap an existing chunk of memory
without providing a custom callback to release that memory then Node
will just use `free()`. In a couple of places Node buffer objects were
constructed from chunks of memory that were allocated with `new`, but
a custom callback to release that memory was omitted, this resulted in
undefined behavior when those buffers were destroyed because `free()`
was used to release memory allocated with `new`.
To avoid undefined behavior the aforementioned buffer objects are now
constructed with a custom callback that safely releases the underlying
chunk of memory.