hotfix: protobuf-c compilation failure
protobuf-c does not compile anymore. Let's handle this a bit better. We now install protobuf and protobuf-c only for the flexran agent. That is, if you want to use the flexran agent, you need to install protobuf/protobuf-c and you do it this way: ./build_oai -I -a (you add -a) Other targets don't need protobuf nor protobuf-c, so it's not installed by the -I command of build_oai, unless you pass -a with -I. Also, we now use protobuf 3.3.0, not 2.6.1. The code has been adapted, a quick test seems to indicate that the system works, but it has not been intensively tested.