Version Control With Subversion Source

Lots more book stuff.

* appb.xml: new appendix documenting cvs2svn.py, to some small degree.

* rcsparse.py: added to cvs2svn/ dir, so people can stop asking where
to get it! please!

* appa.xml (Binary files): add internal binary-diff explanation.

* ch05.xml: expand our explanation of how to run svnserve, and how to
set up ssh tunneling. Also, add a honest comparison of
reasons to run either mod_dav_svn or svnserve.

* ch06.xml (Servers): uncomment the 'svn-tunnel-agent' documentation.

* ch07.xml (RA-SVN): add one more paragraph.