better description for function typedef's params and return

e.g.

```
@typedef {function((ol.Coordinate|undefined)): string}
```

we would need to generate @function @param and @return tags in a plugin for this to work.

But also something is up with the templates, since only if I use the default jsdoc templates the function params will actually show up from a static @function or @callback such as:

```
/**
 * @function xxx requestCallback
 * @param {number} responseCode
 * @param {string} responseMessage
 */

/**
 * This callback is displayed as a global member.
 * @callback requestCallback
 * @param {number} responseCode
 * @param {string} responseMessage
 */
```