Return 401 headers when authentication is required for the api call

lib/api.php

@@ -94,6 +94,8 @@ class OC_API {
 				$response = new OC_OCS_Result(null, 998, 'Api method not found');
 			} 
 		} else {
+			 header('WWW-Authenticate: Basic realm="Authorisation Required"');
+			 header('HTTP/1.0 401 Unauthorized');
 			$response = new OC_OCS_Result(null, 997, 'Unauthorised');
 		}
 		// Send the response