support @SensitiveData -> FLAG_CLEAR_BUF

Allow interfaces to be marked as SensitiveData, so that
transactions to them have data/replies cleared in kernel data.

Bug: 171501998
Test: aidl_integration_test, inspecting source
Change-Id: I89e20235ef587767eea8036bff2f7ac321926718
diff --git a/aidl_language.h b/aidl_language.h
index 675acd6..25709e2 100644
--- a/aidl_language.h
+++ b/aidl_language.h
@@ -170,6 +170,7 @@
     VINTF_STABILITY,
     NULLABLE,
     UTF8_IN_CPP,
+    SENSITIVE_DATA,
     JAVA_PASSTHROUGH,
     JAVA_DERIVE,
     JAVA_ONLY_IMMUTABLE,
@@ -241,6 +242,7 @@
   }
   bool IsNullable() const;
   bool IsUtf8InCpp() const;
+  bool IsSensitiveData() const;
   bool IsVintfStability() const;
   bool IsJavaOnlyImmutable() const;
   bool IsFixedSize() const;