Vendor dependencies for 0.3.0 release

vendor/heapless/src/test_helpers.rs

@@ -0,0 +1,23 @@
+macro_rules! droppable {
+    () => {
+        static COUNT: core::sync::atomic::AtomicI32 = core::sync::atomic::AtomicI32::new(0);
+
+        #[derive(Eq, Ord, PartialEq, PartialOrd)]
+        struct Droppable(i32);
+        impl Droppable {
+            fn new() -> Self {
+                COUNT.fetch_add(1, core::sync::atomic::Ordering::Relaxed);
+                Droppable(Self::count())
+            }
+
+            fn count() -> i32 {
+                COUNT.load(core::sync::atomic::Ordering::Relaxed)
+            }
+        }
+        impl Drop for Droppable {
+            fn drop(&mut self) {
+                COUNT.fetch_sub(1, core::sync::atomic::Ordering::Relaxed);
+            }
+        }
+    };
+}