Shape: fix reading of shapefiles whose .shx is non conformant (the content length of records is different from the one in the .shp) (#5608)

git-svn-id: https://svn.osgeo.org/gdal/trunk@27577 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_travis_macosx