versioner: add extern "C" to tests.

Bug: https://github.com/android-ndk/ndk/issues/440
Test: python run_tests.py
Change-Id: Id893979146bc609a17bd1fa2a6bec6f10dfe4804
diff --git a/tools/versioner/tests/preprocessor/expected/foo.h b/tools/versioner/tests/preprocessor/expected/foo.h
index 73947b2..cb719f0 100644
--- a/tools/versioner/tests/preprocessor/expected/foo.h
+++ b/tools/versioner/tests/preprocessor/expected/foo.h
@@ -1,3 +1,7 @@
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
 int always_available();
 
 int also_always_available() __INTRODUCED_IN(9);
@@ -74,3 +78,7 @@
 int future() __INTRODUCED_IN_FUTURE;
 #endif /* __ANDROID_API__ >= __ANDROID_API_FUTURE__ */
 
+
+#if defined(__cplusplus)
+}
+#endif