Function gio_sys::g_file_copy_async

pub unsafe extern fn g_file_copy_async(source: *mut GFile,
                                       destination: *mut GFile,
                                       flags: GFileCopyFlags,
                                       io_priority: c_int,
                                       cancellable: *mut GCancellable,
                                       progress_callback: GFileProgressCallback,
                                       progress_callback_data: gpointer,
                                       callback: GAsyncReadyCallback,
                                       user_data: gpointer)