patch for contrib/isn

hi all,

currently i am working on a big project for a german bookseller and
publisher. one of the requirements was correct hyphenation of ISBN-13
for about 14.400.000 books in postgresql database. so added support
for hyphenating isbn with the new 979-prefix and additionally added all
missing ranges since year 2006 for isbn with 978-prefix.

patch against HEAD is attached and validated against a lot of previously
wrong and correct hyphenated isbn.

regards, jan