separate side effects from specifier
fixes TDZ for export let/const
bigger bundles are caused by correct export const/let behavior
BREAKING CHANGE: Internal have changed. Plugins could rely on them.
* moved format location into separate file
allow dependencies to report errors too
* NullDependencies do not change the hash
* dependencies can opt-out from `__webpack_require__` param
* apply module syntax plugins earlier
* emit errors if using AMD or CommonJS syntax in harmony modules