check default RasterRead parameters

git-svn-id: https://svn.osgeo.org/gdal/trunk@26585 f0d54148-0727-0410-94bb-9a71ac55c965
default xoff,yoff,xsize,ysize to ReadRaster calls

git-svn-id: https://svn.osgeo.org/gdal/trunk@26586 f0d54148-0727-0410-94bb-9a71ac55c965