[PATCH] DocBook: allow to mark structure members private

Many structures contain both an internal part and one which is part of the API
to other modules.  With this patch it is possible to only include these public
members in the kernel documentation.

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