Version Control With Subversion Source

* src/fr/book/images/ch01dia1.svg,
* src/fr/book/images/ch04dia1.svg
Minor tweaks on the diagrams.

* src/en/book/styles.css
More style tweaks. Dial back in the in-text color changes (to
near-zero). But as a trade-off, color the navigation bars similarly
to the printed book's pinkishpurplish tone.

* src/en/HACKING
Wrap sample <screen> with <informalexample>, too.

Wrap <screen>'s and <programlisting>'s which aren't part of formal
<example>'s with <informalexample>...</informalexample>. (I almost
certainly overlooked -- or underlooked -- something in this commit.)

NOTE: Chapter 9 (the Reference) uses <programlisting> tags around
command syntax. I didn't wrap those.

SIDEBAR: Chapter 9's markup is positively atrocious. I know we were
following the O'Reilly recommendations here, but I kinda want to have
my eyes gouged out after reading even a small chunk of the source for
that chapter, and I pity Fitz, who's logged more hours in this chapter
than the rest of us combined.

* src/en/book/appa-quickstart.xml,
* src/en/book/appb-svn-for-cvs-users.xml,
* src/en/book/appc-webdav.xml,
* src/en/book/ch02-basic-usage.xml,
* src/en/book/ch03-advanced-topics.xml,
* src/en/book/ch04-branching-and-merging.xml,
* src/en/book/ch05-repository-admin.xml,
* src/en/book/ch06-server-configuration.xml,
* src/en/book/ch07-customizing-svn.xml,
* src/en/book/ch08-embedding-svn.xml,
* src/en/book/ch09-reference.xml
Introduce a buuuuuunch of <informalexample> tags.

* src/en/book/styles.css
Tweak HTML styles (mostly around admonishments).

* src/en/book/ch05-repository-admin.xml
(svn.reposadmin.basics.backends.fsfs): Lose reference to delta
direction, and clarify a bit about the commit delay. This
finishes issue #18 ("1.6 change: BDB forward deltas").

* src/en/book/ch05-repository-admin.xml
(svn.reposadmin.maint.diskspace.deltas): Mention rep-sharing,
finishing issue #16 ("New 1.6 feature: FS representation sharing").

Finish Issue #13 ("Spaces in file names in svn:externals").

* src/en/book/ch03-advanced-topics.xml
(svn.advanced.externals): Document the quoting/escape mechanism for
external working copies.

Fix issue #26 ("Document mod_dav_svn environment variables")

* src/en/book/ch06-server-configuration.xml
(svn.serverconfig.httpd.extra.logging): Also note the SVN-REPOS and
SVN-REPOS-NAME environment variables.

One more change for issue #125 ("1.6 change: svn status output (new
7th column)").

* src/en/book/ch02-basic-usage.xml
(svn.tour.cycle.examine.status): "six" -> "seven".