[gdm] (8 commits) ...Merge branch 'gdm-client-single-connection-getter' into 'master'

[Marco Trevisan <marcotrevi src gnome org>]

Summary of changes:

  4d2da18... libgdm: Unref the manager propagated from task
  d3b1cc1... libgdm: Don't double-ref the connection got from task
  1f5678c... libgdm: Don't leak connection on sync re-authentication
  d92f4d9... libgdm: Use auto-pointers and cleanup code
  7782778... libgdb: Try to reuse connections from the available proxies
  a01fc3c... libgdm: Don't save manager address
  aca3d13... libgdm: Return NULL on invalid client instances
  8529e2d... Merge branch 'gdm-client-single-connection-getter' into 'ma