OSM: always use quoting of key/values in other_tags field so as to produce a valid value for PostgreSQL hstore column, even if the value is empty or contains a newline character (#5096)

git-svn-id: https://svn.osgeo.org/gdal/branches/1.10@26051 f0d54148-0727-0410-94bb-9a71ac55c965