Merge the following changes in the English version:

authors.ent 1.65 -> 1.69
advanced-networking/chapter.sgml 1.16 -> 1.17
contrib/chapter.sgml 1.142 -> 1.150
internals/chapter.sgml 1.14 -> 1.15
introduction/chapter.sgml 1.22 -> 1.23
mirrors/chapter.sgml 1.46 -> 1.47
staff/chapter.sgml 1.89 -> 1.93

Submitted by: Shun SUZUKI <si006@ccm.gs.niigata-u.ac.jp>