Shape: in OGRShapeDriver::DeleteDataSource(), delete .cpg file if existing

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@25881 f0d54148-0727-0410-94bb-9a71ac55c965
Shape: avoid excessive memory allocation when issuing REPACK on a huge DBF file

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@25882 f0d54148-0727-0410-94bb-9a71ac55c965