links option ignored in offline mode, even for local links

The `links` property is ignored when offline mode. This may make sense when it generates links to an external server and needs access to its `package-list`. However, it is still ignored when generating links to external javadocs in the local filesystem. This also means that it no longer matches the javadoc `-link` which would accept links to the local filesystem nicely like so:

javadoc -link file:///usr/local/share/doc...