Bug#919467: steam: data loss when switching from Valve's steam package

[Simon McVittie]

Control: block 916303 by -1
Control: tags -1 + patch pending

On Wed, 16 Jan 2019 at 10:46:37 +0000, Simon McVittie wrote:
> I think we can solve this by using a variation of the patch I attached
> to #916303.

See attached. I'll upload this in the next version of steam if there are
no objections.

This is basically my earlier patch from #916303, except that the default
is swapped: it will continue to use ~/.steam as the $STEAMDIR for new
installations, and only use ~/.local/share/Steam (or any other $STEAMDIR)
if that was already set up. This reduces the solution to #916303 to
"swap the default".

    smcv