SXF: fix various random crashes on Windows that were due to the /Zp1 option, forcing packing of structures to 1 byte alignment, but causing issues with OGR core structures. Now the unit tests pass. If structure packing is still necessary, don't do it that way but with local #pragma (#4331)

git-svn-id: https://svn.osgeo.org/gdal/trunk@26772 f0d54148-0727-0410-94bb-9a71ac55c965