pnfsblock: basic extent code

Adds structures and basic create/delete code for extents.

Signed-off-by: Fred Isaman <iisaman@citi.umich.edu>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Zhang Jingwang <Jingwang.Zhang@emc.com>
Signed-off-by: Benny Halevy <bhalevy@tonian.com>
Signed-off-by: Jim Rees <rees@umich.edu>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --cc fs/nfs/blocklayout/Makefile
Simple merge

diff --cc fs/nfs/blocklayout/blocklayout.c
Simple merge

diff --cc fs/nfs/blocklayout/blocklayout.h
Simple merge

diff --cc fs/nfs/blocklayout/extents.c
Simple merge