Fix Guile version checking in the "web" code.

* guix/web.scm (http-fetch): fix Guile version checking. The previous version
would use features from Guile 2.0.9+ when using Guile 2.0.7.

guix refresh: Add '--key-download'.

* guix/gnu-maintenance.scm (download-tarball): Add a 'key-download'
  keyword argument and pass it to 'gnupg-verify*'.  Make
  'archive-type' a keyword argument.
  (package-update): Add a 'key-download' keyword argument.  Pass
  'archive-type' and 'key-download' keyword arguments to
  'download-tarball'.

* guix/gnupg.scm: Import (ice-9 i18n) and (guix ui).
  (gnupg-verify*): Add a 'key-download' keyword argument and adjust
  'gnupg-verify*' to use it.  Make 'server' a keyword argument.

* guix/scripts/refresh.scm (show-help, %options): Add and document
  '--key-download'.
  (update-package): Add a 'key-download' keyword argument and pass it
  to 'package-update'.
  (guix-refresh): Pass 'key-download' to 'update-package'.  Limit
  lines to a maximum of 79 characters.

doc: Mention copyright/license auditing in `HACKING'.

gnu: Add mpg321.

* gnu/packages/mp3.scm (mpg321): New variable.

gnu: Add ALSA-lib; use it.

* gnu/packages/linux.scm (alsa-lib): New variable.
* gnu/packages/oggvorbis.scm (ao): Add ALSA-lib as an input.

gnu: glib: Fix URL.

* gnu/packages/glib.scm (glib): Fix URL.

doc: Update bootstrap-related info in `HACKING'.

gnu: glib: Update to 2.37.1.

* gnu/packages/glib.scm (glib): Update to 2.37.1.  Add Bash and tzdata
  as inputs.  Remove `glib-tests-timezone.patch'.  Augment `pre-build'
  phase to set `TZDIR', `XDG_CACHE_HOME', and to modify makefiles to
  honor $(TESTS_ENVIRONMENT).
* gnu/packages/patches/glib-tests-desktop.patch,
  gnu/packages/patches/glib-tests-homedir.patch: Update.
* gnu/packages/patches/glib-tests-timezone.patch: Remove.
* Makefile.am (dist_patch_DATA): Update accordingly.

gnu: subversion: Download from apache archive site.

* gnu/packages/subversion.scm (subversion): Download from archive.apache.org,
  where versions are kept for a longer period of time.  Previously, we
  downloaded from the mirrors, which keep only the most recent versions.

gnu: plotutils: Add X client libraries as inputs.

* gnu/packages/plotutils.scm (plotutils): Add libx11, libxt, and libxaw
  as inputs.

gnu: Add Privoxy.

* gnu/packages/tor.scm (privoxy): New variable.

packages: Make the `propagated-inputs' field thunked.

* guix/packages.scm (<package>): Make `propagated-inputs' thunked.

gnu: bash-light: Allow cross-compilation.

* gnu/packages/bash.scm (bash-light): Add (guix build gnu-cross-build)
  to #:modules when (%current-target-system) is true.
  Add `bash_cv_job_control_missing=no' to #:configure-flags
  when (%current-target-system) is true.

gnu: Fix `static-package' arguments overriding.

* guix/build-system/gnu.scm (static-package): Call `package-arguments'
  from within the `arguments' field, so it see the
  right (%current-target-system).

gnu: gnutls: Update to 3.2.1.

* gnu/packages/gnutls.scm (gnutls): Update to 3.2.1.

gnu: nettle: Update to 2.7.1.

* gnu/packages/nettle.scm (nettle): Update to 2.7.1.

gnu: automake: Update to 1.13.3.

* gnu/packages/autotools.scm (automake): Update to 1.13.3.

gnu: Add WordNet.

* gnu/packages/wordnet.scm: New file.
* Makefile.am (MODULES): Add it.

gnu: Add Tk.

* gnu/packages/tcl.scm (tk): New variable.

doc: Write about patch submission and packaging guidelines.

* HACKING: Update the command names from `guix-build' to `guix build' & co.
  (Submitting Patches, Packaging Guidelines): New sections.
* doc/guix.texi (Contributing): New section.