xfs: decouple inode and bmap btree header files

Currently the xfs_inode.h header has a dependency on the definition
of the BMAP btree records as the inode fork includes an array of
xfs_bmbt_rec_host_t objects in it's definition.

Move all the btree format definitions from xfs_btree.h,
xfs_bmap_btree.h, xfs_alloc_btree.h and xfs_ialloc_btree.h to
xfs_format.h to continue the process of centralising the on-disk
format definitions. With this done, the xfs inode definitions are no
longer dependent on btree header files.

The enables a massive culling of unnecessary includes, with close to
200 #include directives removed from the XFS kernel code base.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_inode_fork.h b/fs/xfs/xfs_inode_fork.h
index 28661a0..eb329a1 100644
--- a/fs/xfs/xfs_inode_fork.h
+++ b/fs/xfs/xfs_inode_fork.h
@@ -19,6 +19,7 @@
 #define	__XFS_INODE_FORK_H__
 
 struct xfs_inode_log_item;
+struct xfs_dinode;
 
 /*
  * The following xfs_ext_irec_t struct introduces a second (top) level