hook up ErrorType.prototype.constructor = ErrorType, so we can subclass from errors
fix some string interpolations I missed during the CS -> ES6 conversion
if super() references the constructor, just call %super directly.
instead of special casing the constructor, set .prototype.constructor to point to the proper function for classes.
add gc roots for the global template callsite ids
add missing this.filename assignment, lost in CS -> ES6 translation
more ucs2_strrstr hacking
dependent primstr's weren't keeping their parent strings alive
use traceur for class3
add regression test for string#lastIndexOf