Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 g_closure_invoke(Arg1, Arg2, Arg3, Arg4)

 g_is_object(Arg1)

 g_is_value(Arg1)

 g_object_new(Arg1, Arg2, Arg3)

 g_object_get_property(Arg1, Arg2, Arg3)

 g_object_set_property(Arg1, Arg2, Arg3)

 g_object_type(Arg1, Arg2)

 g_param_spec_value_type(Arg1, Arg2)

 g_signal_connect(Arg1, Arg2, Arg3, Arg4, Arg5)

 g_signal_connect_after(Arg1, Arg2, Arg3, Arg4, Arg5)

 g_signal_connect_data(Arg1, Arg2, Arg3, Arg4, Arg5, Arg6)

 g_signal_connect_swapped(Arg1, Arg2, Arg3, Arg4, Arg5)

 g_signal_emit(Arg1, Arg2, Arg3, Arg4)

 g_value_get_boxed(Arg1, Arg2)

 g_value_holds(Arg1, Arg2)

 g_value_init(Arg1, Arg2)

 g_value_set_boxed(Arg1, Arg2)