Update documentation to Docbook 4.5

Update documentation to Docbook 4.5

The package 'docbook-tools' [1] required to format Docbook 3.0 into man pages
has been obsoleted a long time ago and can no longer be downloaded from its
former homepage. Recent versions of that package -- now called 'docbook2X' --,
cannot deal with that old markup format anymore (and don't support the '-w all'
command line switch either). To remedy these issues, all SGML files have been
updated to Docbook 4.5 so that recent versions of docbook2man can process them.

[1] http://sources.redhat.com/docbook-tools/
[2] http://docbook2x.sourceforge.net/

Signed-off-by: Peter Simons <simons@cryp.to>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>