Vendor dependencies for 0.3.0 release

vendor/derive_more/tests/add_assign.rs

@@ -0,0 +1,13 @@
+#![cfg_attr(not(feature = "std"), no_std)]
+#![allow(dead_code)] // some code is tested for type checking only
+
+use derive_more::AddAssign;
+
+#[derive(AddAssign)]
+struct MyInts(i32, i32);
+
+#[derive(AddAssign)]
+struct Point2D {
+    x: i32,
+    y: i32,
+}