d/libostree-1-1.symbols: Add backported repo locking symbols

These are all added with upstream's `LIBOSTREE_2021.3` symbol version so
that packages using the symbols won't need to be rebuilt when ostree
gets updated to that version.

https://phabricator.endlessm.com/T31868

debian/libostree-1-1.symbols

@@ -36,6 +36,7 @@ libostree-1.so.1 libostree-1-1 #MINVER#
  LIBOSTREE_2020.4@LIBOSTREE_2020.4 2020.4
  LIBOSTREE_2020.7@LIBOSTREE_2020.7 2020.7
  LIBOSTREE_2020.8@LIBOSTREE_2020.8 2020.8
+ LIBOSTREE_2021.3@LIBOSTREE_2021.3 2020.8
  ostree_async_progress_copy_state@LIBOSTREE_2019.6 2019.6
  ostree_async_progress_finish@LIBOSTREE_2016.3 2016.4
  ostree_async_progress_get@LIBOSTREE_2017.6 2017.6
@@ -202,6 +203,8 @@ libostree-1.so.1 libostree-1-1 #MINVER#
  ostree_repo_abort_transaction@LIBOSTREE_2016.3 2016.4
  ostree_repo_add_gpg_signature_summary@LIBOSTREE_2016.3 2016.4
  ostree_repo_append_gpg_signature@LIBOSTREE_2016.3 2016.4
+ ostree_repo_auto_lock_cleanup@LIBOSTREE_2021.3 2020.8
+ ostree_repo_auto_lock_push@LIBOSTREE_2021.3 2020.8
  ostree_repo_checkout_at@LIBOSTREE_2016.8 2016.8
  ostree_repo_checkout_at_options_set_devino@LIBOSTREE_2017.13 2017.13
  ostree_repo_checkout_gc@LIBOSTREE_2016.3 2016.4
@@ -306,6 +309,8 @@ libostree-1.so.1 libostree-1-1 #MINVER#
  ostree_repo_load_object_stream@LIBOSTREE_2016.3 2016.4
  ostree_repo_load_variant@LIBOSTREE_2016.3 2016.4
  ostree_repo_load_variant_if_exists@LIBOSTREE_2016.3 2016.4
+ ostree_repo_lock_pop@LIBOSTREE_2021.3 2020.8
+ ostree_repo_lock_push@LIBOSTREE_2021.3 2020.8
  ostree_repo_mark_commit_partial@LIBOSTREE_2017.15 2017.15
  ostree_repo_mark_commit_partial_reason@LIBOSTREE_2019.4 2019.4
  ostree_repo_mode_from_string@LIBOSTREE_2016.3 2016.4