Updated sysctl documentation take #2

Since people didn't like the "many small files" approach, I've moved
it to directories containing index.txt files:

Documentation/sysctl/vm/index.txt
Documentation/sysctl/net/core/index.txt
Documentation/sysctl/net/unix/index.txt
Documentation/sysctl/net/ipv4/index.txt
Documentation/sysctl/net/ipv4/conf/index.txt
Documentation/sysctl/net/ipv4/route/index.txt
Documentation/sysctl/net/ipv4/neigh/index.txt

and so on.

As previously, this moves all sysctl documentation (including
XFS and network) to Documentation/sysctl/*. The patch is
against linus tree and weights more than 200K in size
and is place at: http://www.terra.es/personal/diegocg/sysctl-docs

Comments?