[PATCH] DocBook: revert xmlto use for .ps and .pdf documentation

As xmlto doesn't work for print documentation, we need docbook-utils again for
these targets.

This patch allows the user to choose the method he wants to use.  (I'm still
hoping that someone will fix passivetex ;-)

Signed-off-by: Martin Waitz <tali@admingilde.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>