bug#6995: 24.0.50; get-free-disk-space doesn't return available space in dired

[Glenn Morris]

Thierry Volpiatto wrote:

> The version of get-free-disk-space doesn't show available space in
> dired, please fix it or revert to 23.2 version.
>
> Actually it show:
> total 10120
>
> instead of:
> total used in directory 9,9M available 24G

Allow me to offer more details:

On my system, where my home directory is NFS mounted,

   df -Pk /home/user

returns

  Filesystem         1024-blocks      Used Available Capacity Mounted on
  /real_directory/home/user 461097104 333392304 127704800      73% /home/user

Because the filesystem name is long, the numerical values do not line
up with the column headings. The current code seems to assume that
they do line up. Thus, running dired on "~" gets wrong values for the
total size.