http://hydra.nixos.org/build/3661100

Fixes issue #70.

Grmbl.

Footnote: doing "make dist-gzip dist-xz" doesn't work with Automake;
you have to do "make dist-gzip; dist-xz".  That's because the dist-*
targets delete the temporary distdir at the end.

For several platforms we don't currently have "native" Nix packages
(e.g. Mac OS X and FreeBSD).  This provides the next best thing: a
tarball containing the closure of Nix, plus a simple script
"nix-finish-install" that initialises the Nix database, registers the
paths in the closure as valid, and runs "nix-env -i /path/to/nix" to
initialise the user profile.

The tarball must be unpacked in the root directory.  It creates
/nix/store/... and /usr/bin/nix-finish-install.  Typical installation
is as follows:

  $ cd /
  $ tar xvf /path/to/nix-1.1pre1234_abcdef-x86_64-linux.tar.bz2
  $ nix-finish-install
  (if necessary add ~/.nix-profile/etc/profile.d/nix.sh to the shell
  login scripts)

After this, /usr/bin/nix-finish-install can be deleted, if desired.

The downside to the binary tarball is that it's pretty big (~55 MiB
for x86_64-linux).

http://hydra.nixos.org/build/2602599

Ensuring that the tests work from the build tree requires a growing
number of nasty hacks.  The tests also don't verify that the installed
Nix actually works.  Thus, the tests now require "make install" to
have been run.

Nix now requires SQLite and bzip2 to be pre-installed.  SQLite is
detected using pkg-config.  We required DBD::SQLite anyway, so
depending on SQLite is not a big problem.

The --with-bzip2, --with-openssl and --with-sqlite flags are gone.