Upstream commit 60a61fabb5d9836e69130bf7c07eea206fe20928 2014.09.20 [Jacques] * CAMLparam initializes with Val_unit rather than 0 since ocaml 4.02. Fix a related problem in ml_gobject (Christopher Zimmermann, PR#1425) * Also factorize some code to use Val_option_* ok avsm@