Merge the following from the English version:

1.16 -> 1.24 internals/chapter.sgml
1.25 -> 1.40 security/chapter.sgml

Submitted by: hino@ccm.cl.nec.co.jp
Reviewed by: susumu@wakabaya.net (internals/chapter.sgml)
References: [doc-jp 8081, 8055]

1.20 -> 1.30 ppp-and-slip/chapter.sgml

Submitted by: Murakoshi Naoto <s1991204@cc.musashi.ac.jp>
Reviewed by: susumu@wakabaya.net
References: [doc-jp 8079]