Version Control With Subversion Source

Issue #284: Document the externals definitions comment syntax.

* en/book/ch03-advanced-topics.xml
(svn.advanced.externals): Add to one of the example series an
externals definition comment, plus a paragraph after the first
demonstration which calls out this feature of the syntax
explicitly.

Suggested by: danielsahlberg

* www/index.zh.html
Update email

[fr] fixing typo.

Keeping French branch in sync with English version.

Replace http:// links with https:// and update links when the old target no longer exists.

* en/book/appa-quickstart.xml
(svn.intro.install): s/http/https/ for apache.org

* en/book/appc-webdav.xml
(svn.webdav.clients.standalone.free): www.ics.uci.edu/~webdav redirect to www.davexplorer.org
(svn.webdav.clients.file-explorer-extensions.linux-de): s/http/https/ for gnome.org and kde.org (and kde.org seems to redirect www.k.o to k.o)
(svn.webdav.clients.fs-impl.windows): s/http/https/ for southrivertech.com (and it seems to redirect www.s.c to s.c)
(svn.webdav.clients.fs-impl.linux): s/http/https/ for nongnu.org

* en/book/ch00-preface.xml
(svn.intro.righttool): s/http/https/ for git-scm.com and mercurial-scm.org (and mercurial-scm.org seems to redirect mercurial-scm.org to www.mercurial-scm.org)
(svn.intro.history): s/http/https/ for collab.net and apache.org
(svn.intro.whatsnew): s/http/https/ for apache.org
(svn.preface.free): s/http/https/ for svnbook.red-bean.com

* en/book/ch03-advanced-topics.xml
(svn.advanced.changelists): s/http/https/ for mail.google.com, www.youtube.com and www.flickr.com

* en/book/ch04-branching-and-merging.xml
(svn.branchmerge.basicmerging.reintegrate): s/http/https/ for svnbook.red-bean.com

* en/book/ch06-server-configuration.xml
(svn.serverconfig.httpd): s/http/https/ for apache.org
(svn.serverconfig.httpd.authn.basic): s/http/https/ for apache.org
(svn.serverconfig.httpd.authn.digest): s/http/https/ for apache.org
(svn.serverconfig.httpd.authz.blanket): s/http/https/ for apache.org
(svn.serverconfig.httpd.ssl.server): s/http/https/ for apache.org and openssl.org (and openssl.org seems to redirect openssl.org to www.openssl.org)
(svn.serverconfig.httpd.extra.browsing.syntax): s/http/https/ viewvc.org, trac.edgewall.org and websvnphp.github.io

* en/book/ch08-embedding-svn.xml
(svn.developer.usingapi): s/http/https/ for apache.org
(svn.developer.usingapi.otherlangs): s/http/https/ for swig.org and svnkit.com

Replace old/broken link to Cyrus SASL with the current url.

* en/book/ch06-server-configuration.xml:
(#svn.serverconfig.svnserve.sasl): As above

1.8/zh: minor tuning

Keeping French branch in sync with English version.
Thanks Daniel Shahaf for the additional precision.

1.8/zh: translation of r6052

1.8/zh: merge changes from trunk, translation todo