Cleanup Return object.

- Expose isOk() instead of having to say getStatus().isOk()
- Add 'get' function which checks to make sure content is valid.
- Mark implicit cast operator as deprecated.

Bug: 32744406
Bug: 31348667
Test: hidl_test
Change-Id: I13bfe33b6c1f9b94a372161064a9e913825df959
diff --git a/base/Android.bp b/base/Android.bp
index d990140..f2f5ab0 100644
--- a/base/Android.bp
+++ b/base/Android.bp
@@ -33,6 +33,7 @@
     },
 
     srcs: [
+        "HidlInternal.cpp",
         "HidlSupport.cpp",
         "Status.cpp",
         "TaskRunner.cpp",