GPKG: fix creation of multiple aspatial tables (INSERT OR REPLACE INTO doesn't work properly with a muliple-column unique key with NULL values)

git-svn-id: https://svn.osgeo.org/gdal/trunk@27986 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_travis_macosx