Everything but the codegen

Now I just have to figure out how calls to new_parser_from_tts are
generated, to remove the ext_cx.cfg() parameter when building with
syntax, because I do that manually, the tests pass! The tests pass!

Author: jdub

libbindgen/src/ir/context.rs

@@ -397,7 +397,7 @@ impl<'ctx> BindgenContext<'ctx> {
         let sess = parse::ParseSess::new();
         let mut loader = base::DummyResolver;
         let mut ctx =
-            GenContext(base::ExtCtxt::new(&sess, vec![], cfg, &mut loader));
+            GenContext(base::ExtCtxt::new(&sess, cfg, &mut loader));
 
         ctx.0.bt_push(ExpnInfo {
             call_site: self.span,

libbindgen/src/lib.rs

@@ -8,6 +8,8 @@
 #![cfg_attr(feature = "clippy", feature(plugin))]
 #![cfg_attr(feature = "clippy", plugin(clippy))]
 
+#![cfg_attr(not(feature = "syntex"), feature(rustc_private))]
+
 #![deny(missing_docs)]
 #![deny(warnings)]