gnu: xcursor-themes: Install data into package output directory.

* gnu/packages/xorg.scm (xcursor-themes): Install icons into output directory
    instead of libxcursor.

gnu: Add python2-pyicu.

* gnu/packages/python.scm (python2-pyicu): New variable.

guix package: Sort the list of generation numbers in '--list-generations'.

* guix/scripts/package.scm (generation-numbers): Sort the result.

guix package: Internationalize "Generation" string.

* guix/scripts/package.scm (guix-package): Internationalize generation
  listing.

Thank Cyrill.

pull: Adjust to 'derivation' API change.

Fixes <http://bugs.gnu.org/15428>.
Reported by Cyrill Schenkel <cyrill.schenkel@gmail.com>.

* guix/scripts/pull.scm (guix-pull): 'unpack' returns a single value.

gnu: Add python-simplejson, python2-simplejson.

* gnu/packages/python.scm (python-simplejson, python2-simplejson):
    New variables.

gnu: python2-pysqlite: Fix 'license'.

* gnu/packages/python.scm (python2-pysqlite): Refer to (@ (guix
  licenses) zlib), not to the same-named package.

gnu: QEMU images boots into dmd.

* gnu/system/dmd.scm: New file.
* gnu/system/vm.scm (system-qemu-image): Define dmd services.
  [populate]: Make var/log and etc/group.
  [boot]: Execute dmd directly.
  Add dmd and etc-group as inputs; add the inputs of dmd services.
* gnu-system.am (GNU_SYSTEM_MODULES): Add gnu/system/dmd.scm.

gnu: Add GNU dmd.

* gnu/packages/system.scm (dmd): New variable.

guix package: Add '--list-generations'.

* guix/scripts/package.scm: Import (srfi srfi-19).
  (generation-time, matching-generations): New functions.
  (show-help): Add '--list-generations'.
  (%options): Likewise.
  (guix-package)[process-query]: Add support for '--list-generations'.
* guix/ui.scm: Import (srfi srfi-19) and (ice-9 regex).
  (string->generations, string->duration): New functions.
* tests/guix-package.sh: Test '--list-generations'.
* tests/ui.scm: Import (srfi srfi-19).
  Test 'string->generations' and 'string->duration'.
* doc/guix.texi (Invoking guix-package): Document '--list-generations'.

hydra: Pass the directory name of the Nix checkout.

* build-aux/hydra/guix.scm (hydra-jobs): Extract the 'file-name' item
  from NIX-CHECKOUT, and pass that to 'tarball-package'.

hydra: Fix typo.

* build-aux/hydra/guix.scm (tarball-package): Unquote 'nix-checkout'.

hydra: Add missing import.

* build-aux/hydra/gnu-system.scm, build-aux/hydra/guix.scm: Use (guix
  derivations).

hydra: Return the .drv file names, not the <derivation> objects.

* build-aux/hydra/gnu-system.scm (package->alist): Call
  'derivation-file-name' on the result of 'package-derivation'.
* build-aux/hydra/guix.scm (package->alist): Likewise.

hydra: Point the Git submodule to our local copy.

* build-aux/hydra/guix.scm (tarball-package): Add 'nix-checkout'
  parameter.  Replace 'patch-bootstrap-script' phase by
  'set-nix-module'.
  (hydra-jobs): Get the 'nix' value from ARGUMENTS, and pass it to
  'tarball-package'.

derivations: 'derivation' and related procedures return a single value.

* guix/derivations.scm (derivation->output-path,
  derivation->output-paths): New procedures.
  (derivation-path->output-path): Use 'derivation->output-path'.
  (derivation-path->output-paths): Use 'derivation->output-paths'.
  (derivation): Accept 'derivation?' objects as inputs.  Return a single
  value.
  (build-derivations): New procedure.
  (compiled-modules): Use 'derivation->output-paths'.
  (build-expression->derivation)[source-path]: Add case for when the
  input matches 'derivation?'.
  [prologue]: Accept 'derivation?' objects in INPUTS.
  [mod-dir, go-dir]: Use 'derivation->output-path'.
* guix/download.scm (url-fetch): Adjust to the single-value return.
* guix/packages.scm (package-output): Use 'derivation->output-path'.
* guix/scripts/build.scm (guix-build): When the argument is
  'derivation-path?', pass it through 'read-derivation'.
  Use 'derivation-file-name' to print out the .drv file names, and to
  register them.  Use 'derivation->output-path' instead of
  'derivation-path->output-path'.
* guix/scripts/package.scm (roll-back): Adjust to the single-value
  return.
  (guix-package): Use 'derivation->output-path'.
* guix/ui.scm (show-what-to-build): Adjust to deal with 'derivation?'
  objects instead of .drv file names.
* gnu/system/grub.scm (grub-configuration-file): Use
  'derivation->output-path' instead of 'derivation-path->output-path'.
* gnu/system/vm.scm (qemu-image, system-qemu-image): Likewise.
* tests/builders.scm, tests/derivations.scm, tests/packages.scm,
  tests/store.scm, tests/union.scm: Adjust to the new calling
  convention.
* doc/guix.texi (Defining Packages, The Store, Derivations): Adjust
  accordingly.

tests: Clarify filtering of the "debug" output.

* tests/guix-package.sh: Clearly filter out the "debug" output of
  'gnu-make-boot0'.

derivations: Add a nicer printer.

* guix/derivations.scm (<derivation>): Add a printer.

derivations: Keep the .drv file name in <derivation> objects.

* guix/derivations.scm (<derivation>): Add 'file-name' field.
  (%read-derivation): Use (port-filename DRV-PORT) as the file name for
  the result.
  (derivation): Set the 'file-name' field in the result.
* tests/derivations.scm ("build derivation with 1 source"): Assert that
  'derivation-file-name' returns the right thing.