* configure.ac: Always show the result of checking for Nixpkgs.  Don't
  warn when Nixpkgs is not found.
* Makefile.am (AM_DISTCHECK_CONFIGURE_FLAGS): Remove `--with-nixpkgs'
  flag.
* guix/utils.scm (%nixpkgs-directory): Use either the compile-time or
  the run-time `NIXPKGS' environment variable.
* release.nix (jobs.tarball, jobs.build): Remove `--with-nixpkgs'
  configure flag.
* README: Mark Nixpkgs as optional.

* distro/packages/databases.scm, distro/packages/guile.scm,
  distro/packages/typesetting.scm: Change uses of `nixpkgs-derivation*'
  to `nixpkgs-derivation', to avoid failing at compile-time.

* guix-package.in, tests/guix-package.sh: New files.
* configure.ac: Output `guix-package'.
* Makefile.am (TESTS): Add `tests/guix-package.sh'.
  (bin_SCRIPTS): Add `guix-package'.

* guix-download.in: New file.
* configure.ac: Emit `guix-download' and make it executable.
* Makefile.am (bin_SCRIPTS): Add `guix-download'.
* po/POTFILES.in: Add `guix-download.in'.

* pre-inst-env.in: New file.
* configure.ac: Add it to `AC_CONFIG_FILES' and `AC_CONFIG_COMMANDS'.

configure.ac: Make 'guild' configure check fatal, otherwise one gets 'compile: command not found' during make

* configure.ac: Switch to version 0.1.

* configure.ac: Add `--with-libgcrypt-prefix'.  Substitute `LIBGCRYPT'.

* Makefile.am (.scm.go): Pass $(LIBGCRYPT).

* guix/utils.scm (%libgcrypt): New variable.
  (sha256): Use it.

* Makefile.am (AM_DISTCHECK_CONFIGURE_FLAGS): New variable.
* configure.ac: Define and substitute `NIX_PREFIX'.

* configure.ac: Use Automake's `gnu' option.
* ChangeLog, NEWS: New files.

* configure.ac: Add `AM_GNU_GETTEXT_VERSION'.  Suggested by
  Antono Vasiljev.

* configure.ac: Use "Guix", not "guix", as the package name.

* guix-build.in: New file.

* configure.ac: Emit `guix-build'.  Add `commands-exec'.
* Makefile.am (bin_SCRIPTS): New variable.
* po/POTFILES.in: Add `guix-build.in'.

* Makefile.am (EXTRA_DIST): Add `build-aux/config.rpath'.
  (SUBDIRS, ACLOCAL_AMFLAGS): New variables.

* configure.ac: Use `AM_GNU_GETTEXT'.  Emit `po/Makefile.in'.

* po/Makevars, po/POTFILES.in: New files.

* Makefile.am (.scm.go): Pass `--target=$(host)'.

* configure.ac: Use `AC_CANONICAL_HOST'.

* configure.ac, Makefile.am: New files.