replace

    for (var method in elproto) if (elproto[has](method) && !setproto[has](method)) {
        if (method == "rotate") {
            setproto[method] = (function (methodname) {
                return function () {
                    var arg = arguments;
                    if (arg.length == 1) { // only deg is present, cx and cy are missing
                        var bbox = this.getBBox();
                        arg = [arg[0], (bbox.x+bbox.x2)/2, (bbox.y+bbox.y2)/2];
                    }
                    return this.forEach(function (el) {
                        el[methodname].apply(el, arg);
                    });
                };
            })(method);
        } else if (method == "scale") {
            setproto[method] = (function (methodname) {
                return function () {
                    var arg = arguments;
                    if (arg.length == 2) { // only sx,sy is present, cx and cy are missing
                        var bbox = this.getBBox();
                        arg = [arg[0], arg[1], (bbox.x+bbox.x2)/2, (bbox.y+bbox.y2)/2];
                    }
                    return this.forEach(function (el) {
                        el[methodname].apply(el, arg);
                    });
                };
            })(method);
        } else {
            setproto[method] = (function (methodname) {
                return function () {
                    var arg = arguments;
                    return this.forEach(function (el) {
                        el[methodname].apply(el, arg);
                    });
                };
            })(method);
        }
    }

seach

    for (var method in elproto) if (elproto[has](method) && !setproto[has](method)) {
        setproto[method] = (function (methodname) {
            return function () {
                var arg = arguments;
                return this.forEach(function (el) {
                    el[methodname].apply(el, arg);
                });
            };
        })(method);
    }