Version Control With Subversion Source

- Make valid XHTML 1.0 Strict.
- Display build duration.

* src/tools/build-nightlies (format_duration): New helper function.
(build_begin_time, build_end_time): Timestamp the build.
(output stage): Add DOCTYPE declaration.
Clarify title wording.
Add mandatory type attribute to <style> element.
Add duration to page.
Remove bogus <ul> used for indentation, and use CSS instead.
Add a few blank lines to ease human inspection of the generated XHTML.