ocfs2: Read from an unwritten extent returns zeros

Return an optional extent flags field from our lookup functions and wire up
callers to treat unwritten regions as holes for the purpose of returning
zeros to the user.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

diff --cc fs/ocfs2/alloc.c
Simple merge

diff --cc fs/ocfs2/aops.c
Simple merge

diff --cc fs/ocfs2/dir.c
Simple merge

diff --cc fs/ocfs2/extent_map.c
Simple merge

diff --cc fs/ocfs2/extent_map.h
Simple merge

diff --cc fs/ocfs2/file.c
Simple merge

diff --cc fs/ocfs2/inode.c
Simple merge

diff --cc fs/ocfs2/journal.c
Simple merge

diff --cc fs/ocfs2/namei.c
Simple merge

diff --cc fs/ocfs2/slot_map.c
Simple merge