* Add missing test for early error
* Add missing test for WithBaseObject
* Improve coverage for `new.target`
* Add test for deletion of SuperReference
* Add tests for `in` keyword restrictions
* fixup! Improve coverage for `new.target`
ECMAScript 2015 introduced tail call optimization for function calls
occuring in a number of positions in the grammar. Assert expected
behavior by triggering a large (but configurable) number of recursive
function calls in these positions. Compliant runtimes will execute such
programs without error; non-compliant runtimes are expected to fail
these tests by throwing an error or crashing when system resources are
exhausted.
