tigefa4u projects Trac

* Switch back to the `sys._getframe()` hack in the implementation of `implements()`, for better thread-safety and nesting support (see [http://groups.google.com/group/trac-dev/browse_thread/thread/7bccf999eb3407ed mailing list post]). Also, made `implements` a static method on the `Component` class, which is then aliased to a module-level function.
* Cleaned up imports in `trac.config`, and use `fileobj.write()` instead of `print>>fileobj` when serializing the configuration.

Testing: remove unused PIPE

Testing: use compat for 2.3

Make the nav item to the current admin page an actual link, to accomodate the need to "jump back up" on "deeper" admin pages.

Remove debug logging leftover from r5912.

Tweak fix for #5819, cached changesets being returned in the opposite order if they happen in the same second

Testing: doc fix

Testing: twill will compile the regex for us, and will give a better failure message this way.

Testing: Merge through r5927 from trunk

Move the `open_environment` from `trac.web.main` to `trac.env`. This function is responsible for the thread-safe caching of environments, and automatically performing the check for needed upgrades, features which may be generally useful outside of the web frontend.