Rework build script to use $(!builddate).

The existing Halibut bob script defaults to building a completely
unversioned source tarball. I think building one with the version
format I'm now more or less standardising on (date + VCS id info) is a
more sensible default. So I'm retiring the SNAPSHOT setting, which I
never used anyway, and making the default work like that.


git-svn-id: svn://svn.tartarus.org/sgt@10252 cda61777-01e9-0310-a592-d414129be87e
Remove Subversion expanded keywords everywhere.

The \versionids in the docs are now added by the bob script; the one
in inputs/test.but has been replaced by fixed text (it didn't matter
what it contained anyway, of course, for test purposes), and the one
in misc/halibut.vim has simply been removed (it wasn't actually
expanded by svn anyway - it still had its old CVS value).


git-svn-id: svn://svn.tartarus.org/sgt@10253 cda61777-01e9-0310-a592-d414129be87e
Remove the MD5-based manifest file system.

A long time ago, it seemed like a good idea to arrange that binaries
of Halibut would automatically cease to identify themselves as a
particular upstream version number if any changes were made to the
source code, so that if someone made a local tweak and distributed the
result then I wouldn't get blamed for the results. Since then I've
decided the whole idea is more trouble than it's worth, so I'm
retiring it completely.


git-svn-id: svn://svn.tartarus.org/sgt@10254 cda61777-01e9-0310-a592-d414129be87e