/vsigzip/: reset EOF flag when doing a Seek() (to be POSIX compliant)

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@27048 f0d54148-0727-0410-94bb-9a71ac55c965
KMLSuperOverlay: for single doc case, handle cases where tiles are remote and not local

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@27049 f0d54148-0727-0410-94bb-9a71ac55c965