Dump a TypeError

After more investigation of issue #558, I found that the problem was in the call to `jsDump()`. That method displays all the enumerable properties of the object, but a TypeError's `message` and `name` properties are nonenumerable in at least some environments.

My proposal is to add a special case for objects that have no enumerable properties, and then look for two specific nonenumerable properties: "message" and "name".

It's possible you might want to start by looking at all properties, including nonenumerable ones, but that's too big a change in behaviour for me to propose. That would include things like the `stack` property for exceptions. If you are interested in trying out the more general approach, look at [this sample code][props] for accessing all properties.

[props]: https://developer.mozilla.org/en-US/docs/Enumerability_and_ownership_of_properties#Obtaining_properties_by_enumerability.2Fownership