gnu-maintenance: Add `doc-description' field to <gnu-package-descriptor>.

* guix/gnu-maintenance.scm (%gsrc-package-list-url): New variable.
  (<gnu-package-descriptor>): Add `doc-description' field.
  (official-gnu-packages)[group-package-fields]: Rename to...
  [read-records]: ... this.  Reverse the result.
  [gsrc-description]: New procedure.
  Add the "description" field to the alist passed to `alist->record'.

records: `recutils->alist' recognizes lines starting with a `+'.

* guix/records.scm (%recutils-plus-rx): New variable.
  (recutils->alist): Use it to read + lines.
* tests/records.scm ("recutils->alist with + lines"): New test.

gnu-maintenance: Use `recutils->alist'.

* guix/gnu-maintenance.scm (official-gnu-packages)[group-package-fields]:
  Rewrite in terms of `recutils->alist'.  Remove `state' parameter.
  Specify "doc-url" and "language" as multiple-value keys in the
  `alist->record' call.

records: `alist->record' supports multiple-field occurrences.

* guix/records.scm (alist->record): Add `multiple-value-keys'
  parameter.  Update docstring, and honor it.
* tests/records.scm ("alist->record"): New record.

records: `recutils->alist' recognizes comments.

* guix/records.scm (%recutils-comment-rx): New variable.
  (recutils->alist): Match comments.
* tests/records.scm ("recutils->alist"): Add comments.

records: Add `recutils->alist' for public consumption.

* guix/records.scm (%recutils-field-rx): New variable.
  (recutils->alist): New procedure, formerly known as `fields->alist'.
* guix/scripts/substitute-binary.scm (fields->alist): Use it.
* tests/records.scm ("recutils->alist"): New test.

gnu: libpng: Upgrade to 1.5.17.

* gnu/packages/libpng.scm (libpng): Upgrade to 1.5.17.

list-packages: Write out the HTML page as UTF-8.

* build-aux/list-packages.scm (list-packages): Install the "C" locale.
  Write out as UTF-8.

tests: Fix guix-package.sh in the presence of multiple-output `make'.

* tests/guix-package.sh: For $boot_make_drv, take only the "out" output.
  Reported by Nikita Karetnikov <nikita@karetnikov.org>.

Add `build-aux/list-packages.scm'.

* build-aux/list-packages.scm: New file.
* Makefile.am (EXTRA_DIST): Add it.

Merge branch 'core-updates'

doc: Add "Installing Debugging Files".

* doc/guix.texi (Installing Debugging Files): New node.
  (Packages with Multiple Outputs): Add cross-reference.

doc: Add "Packages with Multiple Outputs" section.

* doc/guix.texi (Packages with Multiple Outputs): New node.
  (Invoking guix package): Refer to it.

tests: Adjust `package-field-location' test for Guile <= 2.0.6.

* tests/packages.scm ("package-field-location"): Check the result of
  `read-at' against both VALUE and (FIELD VALUE).
  Reported by Matthew Lien - 練喆明" <bluet@bluet.org>.

build: Set the umask to 0022 before running the daemon for tests.

* test-env.in: Run "umask 0022" before running the daemon.
  Reported by Matthew Lien - 練喆明 <bluet@bluet.org>

build: Set the umask to 0022 before running the daemon for tests.

* test-env.in: Run "umask 0022" before running the daemon.
  Reported by Matthew Lien - 練喆明 <bluet@bluet.org>

gnu: gettext: Upgrade to 0.18.3.

* gnu/packages/gettext.scm (gettext): Upgrade to 0.18.3.
  Remove patch.  Change `patch-tests' phase to use (which "sh'); keep it
  regardless of whether we're cross compiling.

gnu: tzdata: Upgrade to 2013d.

* gnu/packages/base.scm (tzdata): Upgrade to 2013d.

doc: Move the packaging guidelines to the manual.

* HACKING (Packaging Guidelines): Remove.
* doc/guix.texi (Packaging Guidelines): New node.

doc: Add a "Porting" section.

* HACKING (Porting the Guix distro on a new platform): Remove.
* doc/guix.texi (Porting): New node.  Describe cross-compilation as the
  only approach.