Removed remaining AT_NAME references

This is an amendment to issue #403.  I missed some "at name" references in the last PR.

Review URL: https://github.com/google/traceur-compiler/pull/413

Closes #413.
Clean test list

Review URL: https://github.com/google/traceur-compiler/pull/415

Closes #415.
Make generators not depend on runtime.js

Use RuntimeInliner to generate addIterator and getIterator instead.

To make this work we use a string key for the iterator symbol if
traceur.options.privateNames is false (private names require
runtime.js anyway).