Function glib_sys::g_filename_to_utf8

pub unsafe extern fn g_filename_to_utf8(opsysstring: *mut c_char,
                                        len: ssize_t,
                                        bytes_read: *mut size_t,
                                        bytes_written: *mut size_t,
                                        error: *mut *mut GError)
                                        -> *mut c_char