Remove all of the temporary defines, structures, old compat fuctions, extra fields, etc... that were needed during the conversion to a split set of json_object_* structures.

Clean up the code in json_object_new_* a bit by dropping unnecesary json_object_base variables.

Also try to accomodate formats to explicitly exclude the decimal (e.g. %.0f).

The user might want to use the userdata for something different, so the
serializer should ignore it by default.

Explicitly setting the serializer to json_object_double_to_json_string will
still make it interpret the userdata as a format string.