gnu: add RetroArch.

* gnu/packages/games.scm (retroarch): New variable.

gnu: gdb: Update to 7.8.2.

* gnu/packages/gdb.scm (gdb): Update to 7.8.2.

gnu: nix: Update to 1.8.

* gnu/packages/package-management.scm (nix): Update to 1.8.

gnu: plotutils: Do not propagate libXaw.

* gnu/packages/plotutils.scm (plotutils): Move LIBXAW from
  'propagated-inputs' to 'inputs'.  Add 'snippet'.

gnu: mercurial: Update to 3.2.4.

* gnu/packages/version-control.scm (mercurial): Update to 3.2.4.

gnu: teckit: Add alternate source URL.

Fixes <http://bugs.gnu.org/19600>.

* gnu/packages/fontutils.scm (teckit)[source]: Add Fedora mirror.

gnu: ninja: Disable testcase SubprocessTest.InterruptChild.

* gnu/packages/patches/ninja-tests.patch: New file.
* gnu/packages/ninja.scm (ninja): Add the patch.
* gnu-system.am (dist_patch_DATA): Add it.

packages: Convert source derivations to monadic style.

* guix/packages.scm (origin->derivation): Take body from
  'package-source-derivation', and change it to monadic style.  Expect
  METHOD to a monadic procedure.
  (package-source-derivation): Define in terms of 'origin->derivation'.
* guix/download.scm (url-fetch): Remove 'store' argument.  Remove
  'guile-for-build' variable.  Turn into a monadic procedure.
* guix/git-download.scm (git-fetch): Likewise.
* guix/svn-download.scm (svn-fetch): Likewise.
* tests/builders.scm (url-fetch*): New procedure.
  Change tests to call 'url-fetch*' instead of 'url-fetch'.
* tests/packages.scm ("package-source-derivation, snippet"): Remove
  'store' parameter of 'fetch' and change it to use 'interned-file'
  instead of 'add-to-store'.
* gnu/packages/bootstrap.scm (bootstrap-origin)[boot]: Remove 'store'
  parameter.

monads: Move '%store-monad' and related procedures where they belong.

This turns (guix monads) into a generic module for monads, and moves the
store monad and related monadic procedures in their corresponding
module.

* guix/monads.scm (store-return, store-bind, %store-monad, store-lift,
  text-file, interned-file, package-file, package->derivation,
  package->cross-derivation, origin->derivation, imported-modules,
  compiled, modules, built-derivations, run-with-store): Move to...
* guix/store.scm (store-return, store-bind, %store-monad, store-lift,
  text-file, interned-file): ... here.
  (%guile-for-build): New variable.
  (run-with-store): Moved from monads.scm.  Remove default value for
  #:guile-for-build.
* guix/packages.scm (default-guile): Export.
  (set-guile-for-build): New procedure.
  (package-file, package->derivation, package->cross-derivation,
  origin->derivation): Moved from monads.scm.
* guix/derivations.scm (%guile-for-build): Remove.
  (imported-modules): Rename to...
  (%imported-modules): ... this.
  (compiled-modules): Rename to...
  (%compiled-modules): ... this.
  (built-derivations, imported-modules, compiled-modules): New
  procedures.
* gnu/services/avahi.scm, gnu/services/base.scm, gnu/services/dbus.scm,
  gnu/services/dmd.scm, gnu/services/networking.scm,
  gnu/services/ssh.scm, gnu/services/xorg.scm, gnu/system/install.scm,
  gnu/system/linux-initrd.scm, gnu/system/shadow.scm, guix/download.scm,
  guix/gexp.scm, guix/git-download.scm, guix/profiles.scm,
  guix/svn-download.scm, tests/monads.scm: Adjust imports accordingly.
* guix/monad-repl.scm (default-guile-derivation): New procedure.
  (store-monad-language, run-in-store): Use it.
* build-aux/hydra/gnu-system.scm (qemu-jobs): Add explicit
  'set-guile-for-build' call.
* guix/scripts/archive.scm (derivation-from-expression): Likewise.
* guix/scripts/build.scm (options/resolve-packages): Likewise.
* guix/scripts/environment.scm (guix-environment): Likewise.
* guix/scripts/system.scm (guix-system): Likewise.
* doc/guix.texi (The Store Monad): Adjust module names accordingly.

gnu: Add zerofree.

* gnu/packages/linux.scm (zerofree): New variable.

gnu: e2fsprogs: Install libext2fs.

* gnu/packages/linux.scm (e2fsprogs)[source]: Add 'snippet'.
  [arguments]: Add --enable-elf-shlibs to #:configure-flags.
  Add #:make-flags.

gnu: Add GLEW.

* gnu/packages/gl.scm (glew): New variable.

services: user-processes: Really honor the grace delay.

* gnu/services/base.scm (user-processes-service): Change #:grace-delay
  default value to 4.  Define 'sleep*' and use it.

system: Add iw to '%base-packages'.

* gnu/system.scm (%base-packages): Add IW.

gnu: wireless-tools: Describe it as deprecated.

* gnu/packages/linux.scm (wireless-tools)[description]: Explain that it
  is deprecated in favor of 'iw'.

gnu: guix: Update snapshot.

* gnu/packages/package-management.scm (guix-devel): Update snapshot.
  Remove now-unneeded sub-module stuff in the 'bootstrap' phase.

gnu: Add QPDF.

* gnu/packages/pdf.scm (qpdf): New variable.

gnu: Add iw.

* gnu/packages/linux.scm (iw): New variable.

gnu: libnl: Update to 3.2.25.

* gnu/packages/linux.scm (libnl): Update to 3.2.25.

services: user-processes: Write debugging messages to the output port.

* gnu/services/base.scm (user-processes-service): Write "sending all
  processes..." message to the current output port, not to /dev/console.