Fix AR type cast to mirror quoting

[nikolai-b]

It seems wrong that

SpatialModel.where("ST_DWITHIN(latlon_geo, ?, 500)", geographic_factory.point(-72.099, 42.099)).to_sql

uses the EWKB format but when the query is actually executed it uses to_s which uses the WKT without passing any SRID. This was causing me issues for me with preprepared statements but I couldn't create a simple text. I do think this gem should pass the SRID of bindings though.

I'm not very happy with the test I've written here. I looked .values_for_queries or looking at the arel but the binds haven't been type_cast at this point so I've used explain.