gnu: xfconf: Disable parallel tests. * gnu/packages/xfce.scm (xfconf): Add 'arguments' field.
gnu: Add xfdesktop. * gnu/packages/xfce.scm (xfdesktop): New variable.
gnu: Add xfwm4. * gnu/packages/xfce.scm (xfwm4): New variable.
gnu: Add thunar-volman. * gnu/packages/xfce.scm (thunar-volman): New variable.
gnu: Add thunar. * gnu/packages/xfce.scm (thunar): New variable.
gnu: Add xfce4-settings. * gnu/packages/xfce.scm (xfce4-settings): New variable.
gnu: Add xfce4-session. * gnu/packages/xfce.scm (xfce4-session): New variable.
gnu: Add xfce4-appfinder. * gnu/packages/xfce.scm (xfce4-appfinder): New variable.
gnu: Add xfce4-panel. * gnu/packages/xfce.scm (xfce4-panel): New variable.
gnu: Add tumbler. * gnu/packages/xfce.scm (tumbler): New variable.
gnu: Add garcon. * gnu/packages/xfce.scm (garcon): New variable.
gnu: Add exo. * gnu/packages/xfce.scm (exo): New variable.
gnu: Add libxfce4ui. * gnu/packages/xfce.scm (libxfce4ui): New variable.
gnu: Add xfconf. * gnu/packages/xfce.scm (xfconf): New variable.
gnu: Add libxfce4util. * gnu/packages/xfce.scm (libxfce4util): New variable.
gnu: Add gtk-xfce-engine. * gnu/packages/xfce.scm: New file. * gnu-system.am (GNU_SYSTEM_MODULES): Add it.