compile protobuf files in conan

[Phibedy]

Atm it only works with gcc 4.8,

../liblmscore.so: undefined reference to `google::protobuf::MessageFactory::InternalRegisterGeneratedFile(char const*, void (*)(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&))'
../liblmscore.so: undefined reference to `google::protobuf::internal::WireFormatLite::WriteBytesMaybeAliased(int, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, google::protobuf::io::CodedOutputStream*)'
../liblmscore.so: undefined reference to `google::protobuf::DescriptorPool::FindFileByName(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) const'

memsharded/conan-protobuf#7
memsharded/conan-protobuf#5