[gnome-flashback] (9 commits) Non-fast-forward update to branch wip/systemd-user-units

[Alberts Muktupāvels <muktupavels src gnome org>]

The branch 'wip/systemd-user-units' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  91c751e... data: add systemd user units
  ddb30c6... add --enable-systemd-session configure option

Commits added to the branch:

  6e5b226... notifications: avoid deprecated g_get_current_time (*)
  95715e2... sound-applet: pass GvcMixerControl to GvcStreamStatusIcon (*)
  a23debe... sound-applet: remove unused GObject properties (*)
  f425481... sound-applet: pass GvcMixerControl to GvcChannelBar (*)
  7e75c7b... sound-applet: remove unused gvc_channel_bar_set_size_group (*)
  f3693ee... sound-applet: move code from init & constructor to construc (*)
  b4a15bd... sound-applet: fix critical warnings (*)
  782ce60... data: add systemd user units
  b19ee93... add --enable-systemd-session configure option

(*) This commit already existed in another branch; no separate mail sent