Get syn tests passing with libsyntax instead of syntex
diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index 3d7495d..ae16090 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -1,12 +1,15 @@
 #![allow(dead_code)]
 
 extern crate walkdir;
+extern crate syntax;
 
 use std::env;
 use std::path::Path;
 use std::process::Command;
 use std::u32;
 
+use self::syntax::ast;
+
 use self::walkdir::DirEntry;
 
 macro_rules! errorf {