Function gio_sys::g_subprocess_communicate_utf8_async

pub unsafe extern fn g_subprocess_communicate_utf8_async(subprocess: *mut GSubprocess,
                                                         stdin_buf: *const c_char,
                                                         cancellable: *mut GCancellable,
                                                         callback: GAsyncReadyCallback,
                                                         user_data: gpointer)