preparatory change to making SvXMLEnumMapEntry a template class for the
"UNO scoped enum" change.

But I think its an improvement by itself, there is no need to initialise
these arrays on-demand, the compiler will do that at link time.

Change-Id: I842c16b3ef44b9f5e1f0325b637d3f55f8bb5ebc
Reviewed-on: https://gerrit.libreoffice.org/34721Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>