0.0-6 sig is now generic and works for character, formula and name input.
0.0-5 Now works for primitives.
0.0-4 Separated listing and writing of sigs in to list_sigs/write_sigs.
      write_sigs now defaults to writing to stdout.
      Operators' and assignment fns' sigs wrapped in backquotes.
      Added siglist indexing.
0.0-3 Added sig_report.
0.0-2 Added pkg2env; pattern arg for write_sigs.
0.0-1 First version, include sig, toString.sig, print.sig, write_sigs.
