Version Control With Subversion Source

Better explain what happens when a file is unlocked in chapter 1.

(Discussed with Stefan Sperling)

* en/book/ch06-server-configuration.xml
Update URL of Subversion's source code, wordsmithing a bit as the URL
no longer points to the root of a repository, but a project root
within the ASF's public repository.

Patch by: danielsh

* en/book/ch06-server-configuration.xml
Some random improvements: clarify svn+ssh:// security issue, fix/add
links, clarify man-in-the-middle attack scope.

Patch by: danielsh
(Tweaked by me.)

* en/book/ch03-advanced-topics.xml
Be a little more precise about why Windows programs combine all the
lines of Unix textfile into one.

Suggested by: John Maher <JohnM{__AT__}rotair.com>

Linkify URL of source code repos.

Patch by: danielsh.

Merge r4231 fix from ^/trunk/en.

Merge r4231 fix from ^/trunk/en.

* en/book/ch02-basic-usage.xml
(svn.tour.cycle.revert): Fix issue 154 ("Chp 2, Basic Usage, Fix
your mistakes, svn revert command"). While here, tweak a
neighboring example for added clarity.

Reported (partially) by: smitathaker{__AT__}gmail.com

* Authentication Options, part 1 (cf.
http://www.svnbook.de/ticket/319).

Remove some svn:mergeinfo added in r4227. (The target of the merge
should have been branches/1.7/en, but was instead branches/1.7.)