Importing meteor-node-stubs in a statically analyzable way is important to
ensure all the aliases for built-in Node modules get set up properly. This
does *not* mean that all meteor-node-stubs/defs/* modules will be imported
unconditionally.
Part of #6562.
The implementation of these stubs is controlled by an optional npm package
called meteor-node-stubs, so we can keep iterating on them after releasing
Meteor 1.3, if we need to.
Fixes#6056.