Merge the following from the English version:

1.91 -> 1.92 book.sgml
1.296 -> 1.306 contrib/chapter.sgml
1.56 -> 1.57 cutting-edge/chapter.sgml
1.32 -> 1.33 introduction/chapter.sgml
1.43 -> 1.45 pgpkeys/chapter.sgml
1.158 -> 1.161 staff/chapter.sgml