xfs: reshuffle dir2 headers

Replace the current mess of dir2 headers with just three that have a clear
purpose:

 - xfs_dir2_format.h for all format definitions, including the inline helpers
   to access our variable size structures
 - xfs_dir2_priv.h for all prototypes that are internal to the dir2 code
   and not needed by anything outside of the directory code.  For this
   purpose xfs_da_btree.c, and phase6.c in xfs_repair are considered part
   of the directory code.
 - xfs_dir2.h for the public interface to the directory code

In addition to the reshuffle I have also update the comments to not only
match the new file structure, but also to describe the directory format
better.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff --git a/fs/xfs/xfs_dir2.c b/fs/xfs/xfs_dir2.c
index 0dee578..6effbeb 100644
--- a/fs/xfs/xfs_dir2.c
+++ b/fs/xfs/xfs_dir2.c
@@ -24,20 +24,17 @@
 #include "xfs_trans.h"
 #include "xfs_sb.h"
 #include "xfs_ag.h"
-#include "xfs_dir2.h"
 #include "xfs_mount.h"
 #include "xfs_da_btree.h"
 #include "xfs_bmap_btree.h"
 #include "xfs_alloc_btree.h"
-#include "xfs_dir2_sf.h"
 #include "xfs_dinode.h"
 #include "xfs_inode.h"
 #include "xfs_inode_item.h"
 #include "xfs_bmap.h"
-#include "xfs_dir2_data.h"
-#include "xfs_dir2_leaf.h"
-#include "xfs_dir2_block.h"
-#include "xfs_dir2_node.h"
+#include "xfs_dir2.h"
+#include "xfs_dir2_format.h"
+#include "xfs_dir2_priv.h"
 #include "xfs_error.h"
 #include "xfs_vnodeops.h"
 #include "xfs_trace.h"