Version Control With Subversion Source

* src/tools/Makefile.base
(book-html): Make the html-book target depend on the presence of
the stylesheet and images.

* src/tools/book-dist.py
(main): Check for build dir existence before trying to rename it.

* src/tools/build-nightlies
New script (used on www.svnbook.com).

* src/de/book
Add 'version.xml' to svn:ignore.