Throws: oldIE native Error types, remove String

Handle oldIE native Error types in `throws`.
Remove the String comparison type from `throws`.

Fixes #547.
Closes #579.
Closes #593.

Related to jquery/api.qunitjs.com#54.
To clarify: it was my switching the order of the `else if` branches (to evaluate constructors before Error instances) and addition of type checks that made the internals of this branch become obsolete later on.