ocfs2: btree changes for unwritten extents

Writes to a region marked as unwritten might result in a record split or
merge. We can support splits by making minor changes to the existing insert
code. Merges require left rotations which mostly re-use right rotation
support functions.

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

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

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

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

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

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

diff --cc fs/ocfs2/ocfs2_fs.h
Simple merge