Add (distro) with a package searching facility.

* Makefile.am (MODULES): Add `distro.scm'.

* distro.scm: New file.
* po/POTFILES.in: Add it.

* tests/packages.scm ("find-packages-by-name", "find-packages-by-name
  with version"): New tests.

Gettextize, with GNU Gettext 0.18.1.

* 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.

Add a declarative packaging layer.

* Makefile.am (MODULES): Add `guix/packages.scm' and `distro/base.scm'.
  (TESTS): Add `tests/packages.scm'.
  (EXTRA_DIST): New variable.

* guix/packages.scm, distro/base.scm, tests/packages.scm: New files.

* guix/http.scm (http-fetch): Make `name' an optional argument, to match
  the expectations of `package-source-derivation'.

build: Define $NIXPKGS when compiling.

* Makefile.am (.scm.go): Define $NIXPKGS.

Abstract build systems.

* Makefile.am (MODULES): Add `guix/build-system.scm' and
  `guix/build-system/gnu.scm'.  Remove `guix/gnu-build-system.scm'.

* guix/build-system.scm: New file.
* guix/gnu-build-system.scm: Rename to...
* guix/build-system/gnu.scm: ... this.
  (gnu-build-system): New variable.

* tests/builders.scm: Adjust `use-module' clauses.
  ("gnu-build-system"): New test.

build: Be cross-compilation-ready.

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

* configure.ac: Use `AC_CANONICAL_HOST'.

build: Provide the right include path when building modules.

* Makefile.am (.scm.go): Add missing `-L $(top_srcdir)'.

Build (guix) last.

* Makefile.am (MODULES): Move `guix.scm' last.

Add a build system.

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