Shouldn't add duplicate tags on node tab pages

Some modules add tabs to the node pages (e.g. talk module, which adds tabs as node/nnn/talk). Meta tags currently adds the node tags and description to these pages, which is not ideal, since the description does not reflect these pages and is duplicate (picked up by Google Webmaster Tools) - it would be better for these modules to add their own customized description using the nodewords API (talk module could add "Discussion about ...." for example).

The attached patches for Drupal 5 and 6 nodewords ensure that tags and description are only added to the primary node page, and not subpages.