LU-709 build: clean up LC_NR_PAGECACHE/LC_STATFS_DENTRY_PARAM

LU-709 build: clean up LC_NR_PAGECACHE/LC_STATFS_DENTRY_PARAM

1. nr_pagecache is not exported from 2.6.18 to latest
2. super_operations->statfs takes dentry instead of superblock
   as first parameter since v2.6.18

Signed-off-by: Peng Tao <tao.peng@emc.com>
Change-Id: I93fd5cdd81b83f0896a1305f5b625fa0c82ef515
Reviewed-on: http://review.whamcloud.com/2319
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>