NITF HISTOA TRE: put definition of TRE in conformance with STDI-0002 (App L page 14) and STDI-0006 (Page 57) (patch by bradh, #5572)

git-svn-id: https://svn.osgeo.org/gdal/branches/1.11@27536 f0d54148-0727-0410-94bb-9a71ac55c965