This allows users to build ol3 without anything exposed in the
global namespace. This can e.g. be useful for creating an ol3
AMD module, by simply using a build configuration with
"define('ol',function(){var o={};%output%return o.ol;});" as
"output_wrapper".
This task generates build related metadata for the library based on doc annotations. Since it is about more than writing out exportable symbols, it makes sense to have a more general name.
