build: deprecate use of abcl.implementation.version
Use abcl.version instead, fixing manifests for jar packaging. The usage of abcl.implementation.version is now deprecated as not working for a long time. The intention was that if a given source tree could be unidentified as being under source control by the presence of given revision control system artifacts, the abcl.implementation.version would contain a version derived from the revision control system. To hack around the non-prescriptive nature of Ant, chains of conditional targets had to be created that while might have once worked for Subversion, were going to get increasingly hairy for Mercurial and Git.