Function inet6_opt_append 

pub unsafe extern "C" fn inet6_opt_append(
    __extbuf: *mut c_void,
    __extlen: socklen_t,
    __offset: c_int,
    __type: u8,
    __len: socklen_t,
    __align: u8,
    __databufp: *mut *mut c_void,
) -> c_int