The handshake function is now called internally (even if it doesn't seem
to be required at all), and the version function can be called through
the public api. The format of the version data is changed too.
Using a resizable memory buffer allows to allocate the right amount of
memory inside the backend, avoiding having to know the required buffer
size in advance.
When necessary, an output parameter is added to provide the size
information. Status codes are strictly reserved for providing status
information only.
