[accounts-dialog] (19 commits) ...GTK3 build fixes

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  7820378... Initial port to a control-center panel (*)
  7cdb45c... Only build the panel (*)
  45ca0cc... Only build the panel (*)
  a2ce590... Various fixes (*)
  6f79fb3... Use standard icon names (*)
  e1bc9b3... Not using libunique anymore (*)
  f1ce0f8... Extract the editable label as a separate widget (*)
  e57ffb9... Turn the account type chooser into a standalone widget too (*)
  91f6f2e... Convert the language chooser to the editable combo widget (*)
  23639fc... Fix a case of non-translatable strings (*)
  7853ebf... More replacement of stock_person by avatar-default (*)
  7178e3e... Prevent jumping text (*)
  b8fc3bb... More widgetification (*)
  8b5f7e8... Remove unneeded include (*)
  1d89164... Some cleanups (*)
  5bd7ec3... Use the changes-prevent icon instead of security-medium (*)
  db413ae... Merge branch 'control-center-panel'
  6d66545... Build against GTK3
  5bf2bd5... GTK3 build fixes

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