Handle params according to the param_oids in handle_bind

[ChaosEternal]

Currently the handle_bind code can't support nested array data type, and more seriously, if the parameter is a string contains ',' or '}' , the parameters get is totall wrong.

Maybe we should use "converters" introduced by the "pg8000" project to properly handle this?

[jwills]

Oooh-- point me at it?