Version Control With Subversion Source

* doc/book/book/ch06.xml: update documentation on mod_authz_svn, now
that Sander has added anonymous-auth and SVNParentPath support to
both 1.0.1 and 1.1.

Er. Minor fixemups to revision 8928.

Fix the name of the Subversion IANA service. Noticed by Matthew
Gregan <kinetik@...>.

Book: major update of ch04 branching/merging example.

* ch04.xml: rewrite long-running example in this chapter to use the
recommended 'project root' layout.

* ch06.xml: rename "Using Multiple Servers" section, to clarify subject.

Change book's chapter 4 diagrams to match rewritten chapter.

* book/images/branches.ppt: changed source file chapter 4 diagrams.

* book/images/ch04dia2.png, ch04dia3.png, ch04dia4.png: changed diagrams.

* subversion/mod_authz_svn/INSTALL:
Spelling fix.

* doc/book/book/ch09.xml:
Remove a stutter.

* book/ch04.xml: add sidebar about changesets.

Expand my svn:externals TODO.

* doc/book/TODO: more book todo's.

Add TODO item regarding externals.