which shaves some time off loading complex files.
Note that this class is often used as a superclass, so I checked all of
the subclasses and marked some of them as "does not support hashing"
until they can be independently verified to be safe
Change-Id: Id4187eda8d6145e89e17dc10c2e3113b7a93da85
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/171891
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
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