Add file that should have gone with r26439 (fix the OSR validation to accept the EXTENSION node in DATUM for PROJ4_GRIDS)

git-svn-id: https://svn.osgeo.org/gdal/trunk@26440 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_travis_macosx