gdu assumes directory takes up 1 block when it doesn't (on XFS)

[joliss]

On XFS, small directories can be stored inline in the inode, rather than taking up a block. This is reported correctly by du, but gdu seems to assume that a directory always occupies one block.

~/tmp $ mkdir somedir
~/tmp $ touch somedir/a
~/tmp $ touch somedir/b
~/tmp $ stat somedir | grep Blocks
  Size: 24        	Blocks: 0          IO Block: 4096   directory
~/tmp $ sudo xfs_bmap somedir
somedir: no extents
~/tmp $ du somedir
0	somedir
~/tmp $ gdu -n | grep somedir
    4.0 KiB /somedir

This happens on gdu master (a8b32c).