Add a warning against modifying transactions in a hook script.
Add a warning against modifying transactions in a hook script.

Patch by: Steve Greenland <steveg@lsli.com>
(Tweaked by me.)

* doc/book/book/ch05.xml
  (svn-ch-5-sect-2.1): Warn against modifying transactions in a hook script.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion