Daemon updated to Nix 1.3

[Ludovic Courtès]

Hi,

Commit a53b000 updates the Git submodule for ‘nix-upstream’ to Nix 1.3.
So make sure to run ‘git submodule update’ followed by
./nix/sync-with-upstream to actually use that code.

When you run it on your existing store, the first time you run
guix-build or some other tool, you’ll see this message:

  removing immutable bits from the Nix store (this may take a while)...

It will indeed take a bit of time (a few minutes on an SSD with a
large store.)  More details at:

  http://thread.gmane.org/gmane.linux.distributions.nixos/10055

(Nix 1.3 is just a bug-fix release, see
<http://hydra.nixos.org/build/3668901/download/3/release-notes/>.)

Ludo’.