Use our own namespace for advisory locks.
Use our own namespace for advisory locks.

Switch to using the two-input form of pg_advisory_lock(), so as
to avoid impacting other applications which might happen to lock
just the OID of the table. The REPACK_LOCK_PREFIX_STR is a decimal
version of the first three bytes of
  echo -n "pg_repack" | sha1sum

bwtakacy/pg_repack,mr-mustash/pg_repack,reorg/pg_repack,reorg/pg_repack