gnu: python-matplotlib: Update comments.

* gnu/packages/python.scm (python-matplotlib): Update comments as, with the
  patched 'gobject-introspection', setting LD_LIBRARY_PATH at run time is not
  anymore necessary.  It's still necessary at build time.

gnu: gtk+: Update to 3.14.7.

* gnu/packages/gtk.scm (gtk+): Update to 3.14.7.

gnu: python-matplotlib: Remove python-pillow input.

* gnu/packages/python.scm (python-matplotlib): Remove python-pillow input as
  it currently is broken.

gnu: atk: Update to 2.15.3.

* gnu/packages/gtk.scm (atk): Update to 2.15.3.

gnu: eudev: Add pre-build phase.

* gnu/packages/linux.scm (eudev): Add 'pre-build phase to fix compilation with
  'gobject-introspection' 1.42.0.

gnu: eudev: Update to 2.1.1.

* gnu/packages/linux.scm (eudev): Update to 2.1.1.

gnu: gdk-pixbuf: Update to 2.31.1.

* gnu/packages/gtk.scm (gdk-pixbuf): Update to 2.31.1.

gnu: pango: Update to 1.36.8.

* gnu/packages/gtk.scm (pango): Update to 1.36.8.

gnu: gobject-introspection: Update to 1.42.0 and add new patch.

* gnu/packages/glib.scm (gobject-introspection): Update to version 1.42.0.
  Add patch 'gobject-introspection-absolute-shlib-path.patch' provided by Luca
  Bruno <lucabru@src.gnome.org> for Nix.

doc: Document '%state-monad' and update '%store-monad' description.

* doc/guix.texi (The Store Monad): Document '%state-monad' and related
  procedures.  Describe '%store-monad' as an alias for '%state-monad'.
* guix/monads.scm: Update commentary.

store: Make '%store-monad' an alias for '%state-monad'.

* guix/store.scm (define-alias): New macro.
  (%store-monad, store-return, store-bind): Define as aliases of the
  corresponding %STATE-MONAD part.
  (store-lift, text-file, interned-file): Return STORE as a second
  value.
  (run-with-store): Use 'run-with-state'.
* guix/packages.scm (set-guile-for-build, package-file): Return STORE as
  a second value.
* guix/monads.scm: Remove part of the module commentary.

monads: Add the state monad.

* guix/monads.scm (state-return, state-bind, run-with-state,
  current-state, set-current-state, state-push, state-pop): New
  procedures.
  (%state-monad): New variable.
* tests/monads.scm (%monads): Add %STATE-MONAD.
  (%monad-run): Add 'run-with-state'.
  (values->list): New macro.
  ("set-current-state", "state-push etc."): New tests.

gnu: linux-libre: Update to 3.18.3

* gnu/packages/linux.scm (linux-libre): Update to version 3.18.3.

gnu: rasqal: Update to 0.9.33.

* gnu/packages/rdf.scm (rasqal): Update to 0.9.33.

gnu: raptor2: Update to 2.0.15.

* gnu/packages/rdf.scm (raptor2): Update to 2.0.15.

guix archive: Add -r/--recursive.

* guix/scripts/archive.scm (show-help, %options): Add -r/--recursive.
  (export-from-store): Pass #:recursive? to 'export-paths'.
* doc/guix.texi (Invoking guix archive): Add -r in Emacs example.  Add
  example with ~/.guix-profile.  Document -r/--recursive.

guix archive: Remove unused -r/--root option.

* guix/scripts/archive.scm (%options): Remove -r/--root.

store: Remove unused variable.

* guix/store.scm (export-paths): Remove unused variable 's'.

store: Add #:recursive? parameter to 'export-paths'.

* guix/store.scm (export-paths): Add #:recursive? parameter and honor
  it.
* tests/store.scm ("export/import incomplete", "export/import
  recursive"): New tests.

doc: Mention generation of ECDSA/Ed25519 keys when supported.

* doc/guix.texi (Invoking guix archive): Mention ECDSA/Ed25519 as the
  default type of keys for libgcrypt >= 1.6.0.