Version Control With Subversion Source

* ru/book/ch04.xml
Translation for 'svn.branchmerge.whatis' and 'svn.branchmerge.using' now
finished, start of translation for 'svn.branchmerge.using.create'

Synchronised with en/

* src/en/TODO: Note peg rev syntax change due to issue #2317.

* src/en/book/ch07.xml
(Externals Definitions): Add tip about using explicit revision numbers.

* src/en/TODO
Note the completion of the related TODO.

Finish talking about external diff and merge tools. Whew!

* src/en/TODO
Note completion of the external diff/diff3 section.

* src/en/book/ch07.xml
(Using External Differencing Tools): Add a note about the
interaction between svn:mime-type and diff/merge tools.
(External diff, External diff3): Add examples and flesh out more of
the descriptive text.

* src/en/book/ch07.xml
s/Gnu/GNU/. (Reported by sussman.)

Standardise the <footnote></footnote> formatting in the Norwegian
svnbook.

* src/nb/book/appa.xml
* src/nb/book/ch00.xml
* src/nb/book/ch03.xml
* src/nb/book/ch04.xml
* src/nb/book/ch05.xml
* src/nb/book/ch06.xml
Make <footnote></footnote> formatting consistent.

Finished proofreading of ch04.xml in the Norwegian svnbook.

* src/nb/TRANSLATION-STATUS
Remove "partial" status of ch04.xml .

* src/nb/book/ch04.xml
Tweaks, corrections and beautifying.

Do some work on documenting the use of external differencing tools.

* src/en/TODO
Note partial completion of a TODO item.

* src/en/book/ch07.xml
(Config): Cross-reference the new section.
(Using External Differencing Tools): New section.

Sync the Norwegian book against the English files, r1504:1520.

* src/nb/LAST_UPDATED
Updated by make sync.

* src/nb/book/appa.xml
* src/nb/book/appb.xml
* src/nb/book/ch04.xml
* src/nb/book/ch06.xml
* src/nb/book/ch08.xml
Updated r1517, r1520.

* src/nb/book/ch00.xml
* src/nb/book/ch01.xml
* src/nb/book/ch02.xml
* src/nb/book/ch03.xml
* src/nb/book/ch05.xml
Updated r1520.

* src/nb/book/ch07.xml
Updated r1517, r1518, r1520.

* src/nb/book/ch09.xml
Updated r1519, r1520.