[PATCH] docbook: make a filesystems book

Make a filesystems DocBook book/file by moving all filesystems info from
kernel-api.tmpl.  Will also merge journal-api.tmpl into it soon (with
permission from Roger Gammans).  Localizes filesystem info and reduces size
of the huge (produced) kernel-api output files.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>