With OFFICE-3940 the loext markup got accepted for ODF1.3 (and
the redundant KeyInfo element removed). Make sure manifest parser
can import new markup.

Change-Id: Id3c88654e8e6e0e256cd68fbb43f1ef670849cf7
Reviewed-on: https://gerrit.libreoffice.org/56597
Tested-by: Jenkins
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>