Revise versioning system to be date-based.

I'm going through all my projects and reworking them to avoid
depending on the monotonic integer-valued source control revision
identifier provided by Subversion, so I can migrate everything to git
without my builds and versioning breaking.

ipbt's version number is now of the form YYYYMMDD.vvvvvv, where vvvvvv
is some string of source control information (currently still the
SVN-style "rNNNNN", but free to change in future). The date provides
monotonicity between my official automated builds, and the second
component is the one I'll be most interested in when people send bug
reports.


git-svn-id: svn://svn.tartarus.org/sgt@10259 cda61777-01e9-0310-a592-d414129be87e
Remove some pointless SVN-expanded keywords.

When I migrate to git, these will all become inert, so it's better to
remove them than keep them lying around.


git-svn-id: svn://svn.tartarus.org/sgt@10260 cda61777-01e9-0310-a592-d414129be87e