Move record utilities to (guix records).

* guix/utils.scm (define-record-type*): Move to...
* guix/records.scm: ... here.  New file.
* guix/build-system.scm, guix/packages.scm: Use it.
* guix/gnu-maintenance.scm: Likewise.
  (official-gnu-packages)[alist->record]: Remove.
* guix/scripts/substitute-binary.scm: Likewise.
  (alist->record, object->fields): Remove.
* tests/utils.scm ("define-record-type*", "define-record-type* with
  letrec* behavior", "define-record-type* & inherit",
  "define-record-type* & inherit & letrec* behavior",
  "define-record-type* & thunked", "define-record-type* & thunked &
  default", "define-record-type* & thunked & inherited"): Move to...
* tests/records.scm: ... here.  New file.

release.nix: Revert back to before unchroot experiments.

* release.nix: Revert to commit 4050e5d6cfe8f7af29f10b2f1b3c7febdc10946a.

gnu: guile-reader: Install modules in the right place.

* gnu/packages/guile.scm (guile-reader): Add `arguments' field.

Update `NEWS'.

gnu: Add GNU RCS.

* gnu/packages/bazaar.scm: Rename to...
* gnu/packages/version-control.scm: ... this.
  (rcs): New variable.
* Makefile.am (MODULES): Adjust accordingly.

build: Really clean .log files from SRFI-64.

* Makefile.am (CLEANFILES): Really catch .log files from SRFI-64.

build: Run `tests/guix-gc.sh' last to avoid test failures.

* Makefile.am (tests/guix-gc.log): New target.  This should fix failures
  that occurred with "make check -j" the first time.

gnu: Add Scheme48.

* gnu/packages/scheme.scm (scheme48): New variable.
* gnu/packages/patches/scheme48-tests.patch: New file.
* Makefile.am (dist_patch_DATA): Add it.

gnu: gnupg: Update to 2.0.20.

* gnu/packages/gnupg.scm (gnupg): Update to 2.0.20.

gnu: chicken: Clear description.

* gnu/packages/scheme.scm (chicken): Remove unneeded part of the
  description.

doc: Document "guix download".

* doc/guix.texi (Defining Packages): Linke to "Invoking guix download".
  (Utilities): Add an overview paragraph.
  (Invoking guix download): New node.

gnu: Sync synopses with the Womb.

* gnu/packages/bazaar.scm (bazaar): Use synopsis from the Womb.
* gnu/packages/gv.scm (gv): Likewise.

tests: Fix out-of-source builds.

* tests/nar.scm (%test-dir): Compute relative to `pre-inst-env', which
  is in $top_builddir.

tests: Add `guix hash' test.

* guix/scripts/hash.scm (guix-hash)[eof->null]: New procedure.
  Use it to convert the EOF object to the empty bytevector.
* tests/guix-hash.sh: New file.
* Makefile.am (SH_TESTS): Add it.

Update Nix sub-module.

* nix-upstream: Update to 3a0cc43ac89ae8f778764c9f5e27b361e4986913
  (Nix ~1.5.2).

refresh: Add `--key-server' and `--gpg'.

* guix/scripts/refresh.scm (%options): Add `--key-server' and `--gpg'.
  (show-help): Update accordingly.
  (update-package): New procedure, formerly in `guix-refresh'.
  (guix-refresh): Use it.  Parameterize `%openpgp-key-server' and
  `%gpg-command'.

gnupg: Turn the GPG command name and keyserver into parameters.

* guix/gnupg.scm (%gpg-command): Turn into a SRFI-39 parameter.
  (%openpgp-key-server): Likewise.  Default to pgp.mit.edu, as
  keys.gnupg.net is unreliable.
  Update users.

gnu: Add CHICKEN.

* gnu/packages/scheme.scm (chicken): New variable.

ui: Invite users to try `--help' in the error message.

* guix/ui.scm (show-guix-usage): Mention `guix --help'.
  Suggested by Mark H. Weaver.
  (run-guix-command): Invoke it when a command is not found.
  (guix-main): Adjust accordingly.

Update `NEWS'.