Function SSL_CTX_set_cert_cb_ex 

pub unsafe extern "C" fn SSL_CTX_set_cert_cb_ex(
    ctx: *mut SSL_CTX,
    cb: Option<unsafe extern "C" fn(ssl: *mut SSL, arg: *mut c_void, out_alert: *mut u8) -> c_int>,
    arg: *mut c_void,
)