Added s_sfw_xhrequest flag to indicate XHR request and its special handling.  Changed set_status_to_expired function name to set_forbidden_header to be consistent and clear about the function's purpose.
Added s_sfw_xhrequest flag to indicate XHR request and its special handling.  Changed set_status_to_expired function name to set_forbidden_header to be consistent and clear about the function's purpose.

cjungmann/schemafw,cjungmann/schemafw,cjungmann/schemafw,cjungmann/schemafw,cjungmann/schemafw