test_ogrsf: fix compilation problem with MSVC

git-svn-id: https://svn.osgeo.org/gdal/trunk@26769 f0d54148-0727-0410-94bb-9a71ac55c965
SXF: add explicit padding byte in SXFRecordHeader structure, so that it is 32 bytes with MSVC (#4331)

git-svn-id: https://svn.osgeo.org/gdal/trunk@26770 f0d54148-0727-0410-94bb-9a71ac55c965