Add support for @nullable annotation

Using this annotation will now cause C++ types to be wrapped in
unique_ptr, and by extension be capable of handling null values.

Support extends to all arrays, Strings, Lists, and Parcelables.

Change-Id: I148a3666279c2badcba097b8925e55f8fcecb9c2
Test: Unit tests pass
Bug: 25969194
Signed-off-by: Casey Dahlin <sadmac@google.com>
diff --git a/tests/aidl_test_client.cpp b/tests/aidl_test_client.cpp
index 8236902..7ec1c6f 100644
--- a/tests/aidl_test_client.cpp
+++ b/tests/aidl_test_client.cpp
@@ -26,6 +26,7 @@
 #include "aidl_test_client_parcelables.h"
 #include "aidl_test_client_service_exceptions.h"
 #include "aidl_test_client_primitives.h"
+#include "aidl_test_client_nullables.h"
 
 // libutils:
 using android::OK;
@@ -90,5 +91,7 @@
 
   if (!client_tests::ConfirmServiceSpecificExceptions(service)) return 1;
 
+  if (!android::aidl::tests::client::ConfirmNullables(service)) return 1;
+
   return 0;
 }