Reduce memory usage of XML Events when processing OpenXML documents

Disabling PRESERVE_LOCATION reduces memory consumption of XML Events somewhat.

For the file from https://bitbucket.org/okapiframework/okapi/issues/894 this reduces the memory/heap/”-Xmx” requirement for round trips (on my machine) from 2176M to 1792M (so 384M less)

The memory requirement is unfortunately still unreasonably high and I think there is no easy way to fix that. But using 400M less is a nice win.

In case the XML inside the OpenXML files is broken the error reporting will be less useful with this change because location information is missing. We could make it configurable, would that be useful?