Function gio_sys::g_output_stream_splice_async

pub unsafe extern fn g_output_stream_splice_async(stream: *mut GOutputStream,
                                                  source: *mut GInputStream,
                                                  flags: GOutputStreamSpliceFlags,
                                                  io_priority: c_int,
                                                  cancellable: *mut GCancellable,
                                                  callback: GAsyncReadyCallback,
                                                  user_data: gpointer)