POSIX ACL support for NFSV4 clients

[Aneesh Kumar K.V]

This patch series implement POSIX ACL support for NFSV4 clients
This is achieved by converting the NFSV4 ACL to posix ACL on the
client side. The feature enables to view and modify POSIX ACL
from the client.

default mount options
-----------------
root at nfs1-client:/mnt/# getfacl  test1
# file: test1
# owner: root
# group: root
user::rw-
group::r--
other::r--

root at nfs1-client:/mnt/#

-o posix mount options
---------------------
root at nfs1-client:/mnt/ext4# getfacl  test1
# file: test1
# owner: root
# group: root
user::rw-
user:root:r--
group::r--
mask::r--
other::r--

root at nfs1-client:/mnt/ext4#
root at nfs1-client:/mnt/ext4#  setfacl -m u:root:w test1
root at nfs1-client:/mnt/ext4# getfacl  test1
# file: test1
# owner: root
# group: root
user::rw-
user:root:-w-
group::r--
mask::rw-
other::r--

root at nfs1-client:/mnt/ext4#
root at nfs1-client:/mnt/ext4#  setfacl -m u:root:r test1
root at nfs1-client:/mnt/ext4# getfacl  test1
# file: test1
# owner: root
# group: root
user::rw-
user:root:r--
group::r--
mask::r--
other::r--

Since we are using NFSV4 ACL format between client and server the posix ACL
mask also get updated when are updating info about the user.

Patches are on top of 2.6.30

-aneesh