If a format id in the system metadata is registered in the xml_catalog table, we will use the schema location for the format id to validate the xml instance;otherwise, we will use our previous way.
Merge 1.9.2 changes back into the trunk
Correct the pathing for the schema directories based on OS. Leave them in the database with linux style paths (forward slashes) since the values are also used to create urls.
Get the file name from the system_id, handling cases where the id starts with http
Object to hold information about a single xml schema.