tigefa4u projects Trac

InterTrac branch: some enhancements for the InterWiki support
* InterWiki definitions in InterMapTxt support trailing comments
(which are subsequently shown in links titles)
* added `Trac` in InterMapTxt, to demonstrate the above feature
and also how to pass multiple arguments to InterWiki links (#1414)

InterTrac: merged with TracDiff (log:branches/cboos-dev/anydiff-branch#2088:2095)

TracDiff: unified diffs produced by Trac now correctly support added files

TracDiff:
* The ''Restricted Changeset'' view is now accessed through the `ChangesetModule`
* some minor cosmetic fixes

TracDiff: changed the Web interface for generalized diffs.

Now, the browser has a ''Diff ...'' button which leads to a page
containing a simple form with 4 text fields, enabling the
selection of the base path/rev and target path/rev.

TracDiff: access to the ''Restricted Changeset'' mode was broken

TracDiff:
* removed a few `print` statements
* clarified implementation notes for the `ArbitraryDiffModule`

TracDiff: refactored `ChangesetModule` and `DiffModule` to take advantage of [2086]: they now both inherit from the `AbstractDiffModule` class

TracDiff: merged with trunk (log:trunk#2039:2088)

Fix syntax error introduced in [2084].