* Remove EventListener fbjs utility
EventListener normalizes event subscription for <= IE8. This is no
longer necessary. element.addEventListener is sufficient.
* Remove an extra allocation for open source bundles
* Split into two functions to avoid extra runtime checks
* Revert unrelated changes
* Use `this` inside invokeGuardedCallback
It's slightly odd but that's exactly how our www fork works.
Might as well do it in the open source version to make it clear we rely on context here.
* Move invokeGuardedCallback into a separate file
This lets us introduce forks for it.
* Add a www fork for invokeGuardedCallback
* Fix Flow
* Unify the way we fork modules
* Replace rollup-plugin-alias with our own plugin
This does exactly what we need and doesn't suffer from https://github.com/rollup/rollup-plugin-alias/issues/34.
* Move the new plugin to its own file
* Rename variable for consistency
I settled on calling them "forks" since we already have a different concept of "shims".
* Move fork config into its own file
