Revision 5

Import vocabularies from Explicator repository, breaking them into 
  separate subdirectories of src/.  There's a certain amount of
  duplication of stuff in the respective src/*/Makefile.in, but this
  is (only?) because these have all come from the same place, so start
  more-or-less identical, and they'll likely diverge at least a little
  in future.
Rework build system, so that all configuration (version number,
  release date, etc) now happens within configure.ac.