Don't use deprecated method to create compiletest config

tests/cfail.rs

@@ -3,10 +3,11 @@ extern crate compiletest_rs as compiletest;
 use std::path::PathBuf;
 
 use compiletest::common::Mode;
+use compiletest::Config;
 
 #[test]
 fn cfail() {
-    let mut config = compiletest::default_config();
+    let mut config = Config::default();
     config.mode = Mode::CompileFail;
     config.src_base = PathBuf::from(format!("tests/cfail"));
     config.target_rustcflags = Some(