Version Control With Subversion Source

* src/en/book/ch04-branching-and-merging.xml
Markup corrections only.

* src/en/book/ch04-branching-and-merging.xml
(svn.branchmerge.nomergedata): Tweak wording a bit, we merge
from a target's history, not to it.

Finish issue #74 ('Term "natural history" lacks definition/
explanation').

* src/en/book/ch04-branching-and-merging.xml
(svn.branchmerge.nomergedata): Add a sidebar with a brief
description of natural history/implicit mergeinfo. Resist
urge to over-explain.

* src/en/book/ch06-server-configuration.xml
(svn.serverconfig.httpd.ssl): Reorganize and expand the SSL
documentation.

Patch by: quinntaylor@...
(Incorporating matererial from christophe.nanteuil@...)
(Tweaked by me.)

Relocate a book section.

* src/en/book/ch06-server-configuration.xml
(svn.serverconfig.httpd.authn): Add a tip which points to the SSL
section.
(svn.serverconfig.httpd.ssl): Move this section down below the
Authentation section.

Patch by: quinntaylor@...
(Tweaked by me.)

* src/en/book/ch03-advanced-topics.xml
Minor typo fix.

Patch by: Mathias Weinert <wein@...>

For issue #110 ("HTML version fails to load correctly"), just dictate
that we should use our own local draft.png image. Leave nothing to
chance.

* src/en/stylesheets/custom-html-stylesheet.xsl
Set the draft.watermark.image property value.

Fix (I hope) issue #110 ("HTML version fails to load correctly").

* src/en/book/images/draft.png
New file, apparently required by XSLT template sets which refer to
'images/draft.png' rather than to the canonical web-located image.

Finish issue #25 ("Blocking Merge Unaware Clients").

* src/en/book/ch04-branching-and-merging.xml
(svn.branchmerge.advanced.pre1.5clients): Give a sample start-commit
hook script which blocks commits from merge-tracking-unaware
clients.

* src/en/book/ch09-reference.xml
Oops! Syntax error fix.