Remove dependency on Subversion in build script.

This is the very minimum change of just replacing r$(revision) with
the new VCS-agnostic $(vcsid). The resulting non-release version
numbers are not helpful (but then, I don't publish non-release
snapshots of Enigma), and the build system is very outdated in other
ways and would probably need bringing properly up to date if I ever
intended to do more real work on this program (but then, I don't,
because I consider it obsoleted by Chroma).


git-svn-id: svn://svn.tartarus.org/sgt@10249 cda61777-01e9-0310-a592-d414129be87e