OZI Map: retrieve the image filename in a case insensitive way (#5593)

git-svn-id: https://svn.osgeo.org/gdal/trunk@27559 f0d54148-0727-0410-94bb-9a71ac55c965
OZI .ozf2/.ozf3: remove .map header detection from Identify() since this is actually handled by the MAP driver

git-svn-id: https://svn.osgeo.org/gdal/trunk@27561 f0d54148-0727-0410-94bb-9a71ac55c965