Throws: support for oldIE native Error types

Handle oldIE native Error types in `throws`.
~~Remove the String comparison type from `throws`.~~ _(see #604)_

Fixes #547.
Closes #579.
Closes #593.

Related to jquery/api.qunitjs.com#54.
Do we really need this? I know it's here for consistency, but I think we can drop it and also for the other assert methods.

We may probably address it in other issue but as we have the api documentation these comments are useless, IMHO.