(*) When passing a part of a global static data to XMLPropertiesOOoTContext_Impl,
just store a reference to it instead of copying

(*) Simplify the OOo2OasisTransformer constructor and call sites to make the const-ness work

Change-Id: I012d638cfd9266ed3514164e84b381d0d577f821
Reviewed-on: https://gerrit.libreoffice.org/57853
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>