function makeLonghand(item, data) {
    switch (item.instruction) {
        case 's': item.instruction = 'c'; break;
        case 't': item.instruction = 'q'; break;
    }
    item.data.unshift(data[data.length - 2] - data[data.length - 4], data[data.length - 1] - data[data.length - 3]);
    return item;
}
Converts next curve from shorthand to full form using the current curve data.

@param {Object} item curve to convert
@param {Array} data current curve data