Don't barf when installing as root

Fix building without a garbage collector

http://hydra.nixos.org/build/6695350

Update release notes

Update release notes for Nix 1.5.3

Bump release date

Handle systems without lutimes() or lchown()

Handle hard links to other files in the output

Update release notes

Delete a left-over trash directory before doing a GC

Fix manual generation

Grmbl.