gnu: Add numpy.

* gnu/packages/python.scm (python-numpy, python2-numpy): New variables.
gnu: move xorg to xdisorg

* gnu/packages/xorg.scm (xeyes, pixman, libdrm, libdrm-2.4.33, mtdev):
  Move to ...
* gnu/packages/xdisorg.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.
gnu: Add xclip.

* gnu/packages/xdisorg.scm (xclip): New variable.
gnu: subversion: Fix libtool wrapper execution in hooks.

* gnu/packages/version-control.scm (subversion)[arguments]: New
  'patch-libtool-wrapper-ls phase.
gnu: python: Add sqlite input.

* gnu/packages/patches/python-sqlite-3.8.4-test-fix.patch,
  gnu/packages/patches/python2-sqlite-3.8.4-test-fix.patch: New patches.
* gnu-system.am (dist_patch_DATA): Add them.
* gnu/packages/python.scm (python-2)[source]: Add patch.
  [inputs]: Add sqlite.
  (python)[source]: Add patch.
gnu: Add python-sqlalchemy.

* gnu/packages/python.scm (python-sqlalchemy, python2-sqlalchemy): New
  variables.
gnu: Add python-pillow.

* gnu/packages/python.scm (python-pillow, python2-pillow): New variables.
gnu: Add python-distutils-extra.

* gnu/packages/python.scm (python-distutils-extra, python2-distutils-extra):
  New variables.
gnu: Add python-elib.intl.

* gnu/packages/python.scm (python-elib.intl, python2-elib.intl): New
  variables.
gnu: Add python-pycairo.

* gnu/packages/gtk.scm (python-pycairo, python2-py2cairo): New variables.
gnu: Add python-pygobject.

* gnu/packages/patches/python2-pygobject-2-gi-info-type-error-domain.patch:
  New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/packages/glib.scm (python-pygobject, python2-pygobject-2): New
  variables.
gnu: Add python2-pygtk.

* gnu/packages/gtk.scm (python2-pygtk): New variable.
gnu: Add gourmet.

* gnu/packages/nutrition.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.
guix system: Use 'mbegin' for 'install'.

* guix/scripts/system.scm (install): Use 'mbegin'.  Lift FORMAT and
  POPULATE-ROOT-FILE-SYSTEM, and use the result.
monads: Add 'mwhen' and 'munless'.

* guix/monads.scm (mbegin): Add special '%current-monad' syntactic
  keyword.
  (mwhen, munless): New macros.
monads: Add 'lift0'.

* guix/monads.scm (lift0): New variable.
doc: Adjust misleading 'user-account' example.

Reported by Sleep_Walker on #guix.

* doc/guix.texi (Using the Configuration System): Remove numeric UID and
  GID from example.
derivations: Export 'derivation-builder'.

* guix/derivations.scm: Export 'derivation-builder'.
packages: Use the target's system Guile when downloading patches.

* guix/packages.scm (patch-and-repack)[patch-inputs]: Pass SYSTEM in
  'package-source-derivation' call.
gnu: Add missing uses of (gnu packages xdisorg).

This is a followup to 3c156c8.

* gnu/packages/gtk.scm: Use (gnu packages xdisorg).
* gnu/packages/xorg.scm: Likewise.