Added Bindgen names to objective-c pointer return types

* Took advantage of the repr transparent to use Bindgen return type
  names.
* Updated unit tests and book

Author: simlay

src/codegen/mod.rs

@@ -3464,18 +3464,23 @@ impl TryToRustTy for Type {
 
                 let inner =
                     inner.into_resolver().through_type_refs().resolve(ctx);
+                let is_objc_pointer = if let Some(ty) = inner.kind().as_type() {
+                    match ty.kind() {
+                        TypeKind::ObjCInterface(..) => true,
+                        _ => false,
+                    }
+                } else {
+                    false
+                };
                 let inner_ty = inner.expect_type();
 
-                let is_objc_pointer = inner.kind().as_type().map_or(false, |ty| {
-                    match ty.kind() {
-                        TypeKind::ObjCInterface(..) => {
-                            true
-                        },
-                        _ => {
-                            false
+                let is_objc_pointer =
+                    inner.kind().as_type().map_or(false, |ty| {
+                        match ty.kind() {
+                            TypeKind::ObjCInterface(..) => true,
+                            _ => false,
                         }
-                    }
-                });
+                    });
 
                 // Regardless if we can properly represent the inner type, we
                 // should always generate a proper pointer here, so use