Thank you for your pull request! Before this is merged we need some tests for the feature, and since we have the tests in a separate repository (https://bitbucket.org/jastadd/jastadd-test), it would be nice if you could make a separate pull request for that repo with one or two tests.
The List template already has an addAll() method which takes a java.util.Collection argument. Since Collection extends Iterable it seems like a better idea to just refactor the existing method to use Iterable instead.
There is however a lack of tests for the addAll() method. I will ad a few tests for that.
Edit: I found an existing test for List.addAll(): tests/ast/list05