Merge with Debian 3.20.1-1

* Dropped changes:
  - debian/gnome-keyring.conf, debian/gnome-keyring-ssh.conf:
    + Provide upstart user session jobs.
  - debian/rules, debian/*.override:
    + Disable XDG autostart when we're using upstart.
  - patches applied in new release:
    - 0001-Look-for-both-dlopen-and-dlsym-when-configuring.patch:
      + Fix finding dlopen and dlsym in the build, fixing FTBFS.
    - 0002-pam-Pass-the-correct-argc-to-gkr_pam_client_run_oper.patch:
      + Fix null pointer dereference when no password is supplied, e.g. in
        lightdm --test-mode.
    - 0001-Die-if-the-XDG-session-we-were-started-under-goes-aw.patch:
      + Cherry-pick upstream patch to track our login session and exit if
        that ends. This means that gnome-keyring gets cleaned up properly
        on logout under dbus-user-session.