* Merge from Debian unstable, remaining Ubuntu changes:
  - debian/patches:
    + xubuntu_ignore-gdm-lang.patch: do not set $LANG to $GDM_LANG, there's
      already an xsession script to do that, and $GDM_LANG might not contain
      a valid locale code.
    + xubuntu_set-xdg-current-desktop.patch: added. Taken from xfce4-utils,
      export XDG_CURRENT_DESKTOP=XFCE, can be useful with alacarte and
      gnome-menus.
    + debian/patches/xubuntu_runtime-logind-support.patch:
      Check for logind support at runtime
  - Add startxfce4.user-session.upstart
* Drop xflock4-light-locker-support.patch, fixed in debian
* debian/patches:
  - 02_add-light-locker-to-xflock4 added, add light-locker support to
    xflock4 now that it's in Jessie.                          closes: #757649