ocfs2: Write support for directories with inline data

Create all new directories with OCFS2_INLINE_DATA_FL and the inline data
bytes formatted as an empty directory. Inode size field reflects the actual
amount of inline data available, which makes searching for dirent space
very similar to the regular directory search.

Inline-data directories are automatically pushed out to extents on any
insert request which is too large for the available space.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Reviewed-by: Joel Becker <joel.becker@oracle.com>