RawRasterBand::IRasterIO(): add special behaviour to avoid going to block based IO when the dataset has INTERLEAVE=PIXEL and is elligible to direct I/O access pattern

git-svn-id: https://svn.osgeo.org/gdal/trunk@26898 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_travis_macosx