* Fix infinite loop: module.exports alias detection
Previously, module.exports alias detection in the binder could enter an
infinite recursion. Now it does not.
Notably, there are *two* safeguards: a counter limiter that I set at
100, and an already-seen set. I actually prefer the counter limiter code
because it's foolproof and uses less memory. But it takes 100
iterations to escape from loops.
* fix space lint
* Remove already-seen map