Various 'stage' related improvements.

- Require @module.rule syntax for value of the <tag> feature.
- Don't support change of name in 'stage'.
- Cleanup in 'stage'.


[SVN r26782]

tools/build

@@ -1 +1 @@
-Subproject commit c5acb666917370d84485e3bc564202da918a35ba
+Subproject commit 84334a4cd0f36a735ce53f8d258d3f6a15e29dc0