* doc/book/book/ch05.xml: Fix typo.
* doc/book/book/ch06.xml: Remove stuttered comma.
* doc/book/book/ch08.xml:
- Add missing word "to".
- Use the word "custom" instead of "proprietary" to describe the
ra_svn protocol, and modernize the description of Subversion's
use of WebDAV, both after consultation with Mike.
- In the "Effective Pool Usage" example, actually clear the pool
at the top of the loop, like the comment says, and destroy the
subpool immediately after the loop, which is what most of our
code does.
- Add slashes to the ends of some URLs.
