Vendor dependencies

Let's see how I like this workflow.

vendor/syn/tests/test_size.rs

@@ -0,0 +1,29 @@
+#![cfg(target_pointer_width = "64")]
+
+use std::mem;
+use syn::{Expr, Item, Lit, Pat, Type};
+
+#[test]
+fn test_expr_size() {
+    assert_eq!(mem::size_of::<Expr>(), 272);
+}
+
+#[test]
+fn test_item_size() {
+    assert_eq!(mem::size_of::<Item>(), 320);
+}
+
+#[test]
+fn test_type_size() {
+    assert_eq!(mem::size_of::<Type>(), 288);
+}
+
+#[test]
+fn test_pat_size() {
+    assert_eq!(mem::size_of::<Pat>(), 144);
+}
+
+#[test]
+fn test_lit_size() {
+    assert_eq!(mem::size_of::<Lit>(), 32);
+}