fix global escodegen reference in entrypoint.js

[crsmithdev]

See https://github.com/estools/escodegen/issues/244.

Attempting to use the release-built escodegen.browser.js fails on import because escodegen in entry-point.js is not defined.

Alternatively, it may be better to eliminate entry-point.js entirely, as since it isn't part of the NPM version, it is impossible to run npm run-script build unless cloning from source.

[michaelficarra]

I don't understand. If global is actually a reference to your global object, that escodegen reference shouldn't cause a ReferenceError.