Update protobuf submodule to 3.0.0-beta-4
Which has the fix for oneofs when using dynamic frameworks in ObjectiveC
diff --git a/examples/cpp/helloworld/Makefile b/examples/cpp/helloworld/Makefile
index b45b3c7..8e6bd96 100644
--- a/examples/cpp/helloworld/Makefile
+++ b/examples/cpp/helloworld/Makefile
@@ -97,7 +97,7 @@
@echo "Please install Google protocol buffers 3.0.0 and its compiler."
@echo "You can find it here:"
@echo
- @echo " https://github.com/google/protobuf/releases/tag/v3.0.0-beta-3.3"
+ @echo " https://github.com/google/protobuf/releases/tag/v3.0.0-beta-4"
@echo
@echo "Here is what I get when trying to evaluate your version of protoc:"
@echo