* bootstrap: Always run "git submodule init".  Run
  `nix/sync-with-upstream'.
  Reported by Nikita Karetnikov and Andreas Enge.

* bootstrap, nix/sync-with-upstream: New files.
* Makefile.am (EXTRA_DIST): Add `bootstrap'.
* daemon.am (EXTRA_DIST): Add `nix/sync-with-upstream'.