New directories are placed in different AGs where possible

Watch the inode numbers as directory inodes are created:

> mkdir a b
> ls -li total 0
     131 drwxr-xr-x 2 sjv users 6 2006-10-20 12:12 a
33554624 drwxr-xr-x 2 sjv users 6 2006-10-20 12:12 b