- added Dummy file Docs/manual_toc.html to make "make dist" happy if the
   real manual.texi has not been copied into Docs/ (which would make sure
   a "real" manual_toc.html would be created
 - fixed symlinking in the bdb subdirectory (docs are not included anyway)
 - added dist-hook to Makefile.am to remove superfluous SCCS directories
   from the source distribution