Fall back to '@@iterator' in for-of loop.
Fall back to '@@iterator' in for-of loop.

Regenerator's for-of implementation doesn't play nice with other
code that uses `'@@iterator'` to "polyfill" iterables. This would fix
it.

rafaelstz/regenerator,kittens/regenerator,kittens/regenerator,Jericho25/regenerator,sebmck/regenerator,Jericho25/regenerator,facebook/regenerator,rafaelstz/regenerator,liviuignat/regenerator,sebmck/regenerator,juliocanares/regenerator,RReverser/js-goto-transpiler,RReverser/js-goto-transpiler,liviuignat/regenerator,juliocanares/regenerator,facebook/regenerator,facebook/regenerator