tigefa4u projects Trac

* Reenable the use of the `htdocs_location` for specifying the URL of the main static resources (source:trunk/trac/htdocs)..)
This should make it easier to deploy the Trac CGI on web servers that don't provide the configurability of Apache. Also,
it enables a group of Trac projects to use the same URL namespace for the resouces, thereby improving the cacheability of
those resources by the user agent.
* Remove the `diff/tab_width` option from the default config. This setting is deprecated in favor of `mimeview/tab_width`.

Escape ticket values in the query view for tickets that no longer match the original criteria. Closes #2243.

Fix layout bug in changeset view for empty log messages. Closes #1983.

Hack for getting the first item of the TracGuide TOC being highighted in IE/Win. Closes #1169.

Fix usage of custom ticket fields in query module for PostgreSQL. Closes #2164.

Make sure the timestamp saved in the ticket change history is an integer. Fixes #2208.

Grr... don't know where I got the idea that the standard escape mechanism wouldn't work for TracLinks... Reverted r2402 (except for the unit-tests, of course) and partially r2394 concerning this aspect.

Usage of the "!" prefix in front of a TracLinks escapes it (both `shref` and `lhref` forms). Fixes #2251.

Explicitely specify the allowed characters that can start and end TracLinks (`shref` form). Should fix #2240 and probably also #1153.

fall back on legacy `base64` interface on Python < 2.4