[PATCH] Docbook: use custom stylesheet

With the custom stylesheet, functions are rendered using ANSI-C syntax and
xmlto is a bit quieter.

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