function in param name causes problems

Something like this:

```
@signature `can-EVENT='{functionKey [argKey..] [hashName=hashKey..]}'`

Specify a callback function to be called on a particular event. You can create your own special event types.

@param {String} EVENT A event name like `click` or `keyup`. If you are
using jQuery, you can listen to jQuery special events too.

@param {can.stache.key} functionKey A named key value in the current scope. The value
should be a function.

@param {can.stache.key} [argKey...] Blah
```

The functionKey argument is not displayed right.

Start by reproducing the documented @signature example containing functionKey, then inspect the documentjs parsing and rendering path for that argument. Compare the displayed functionKey argument with the source example; done means the argument is displayed correctly.

Written by the indexing model from the issue text.