Merge following changes in the English version.

1.90 -> 1.91 book.sgml
1.146 -> 1.149 staff/chapter.sgml
1.37 -> 1.40 pgpkeys/chapter.sgml
1.34 -> 1.35 hw/chapter.sgml
1.52 -> 1.53 cutting-edge/chapter.sgml
1.109 -> 1.112 authors.ent