message: [c++] Fix missing Protocols type arg in Merger
diff: @@ -18,7 +18,7 @@ namespace bond
  template <typename T, typename Writer, typename Protocols = BuiltInProtocols>
  class Merger
  - : public Serializer<Writer>
  + : public Serializer<Writer, Protocols>
  {
  public:
  typedef T FastPathType;
  @@ -30,7 +30,7 @@ public:
  using Serializer<Writer, Protocols>::Container;
  Merger(const T& var, Writer& output, bool base = false)
  - : Serializer<Writer>(output, base),
  + : Serializer<Writer, Protocols>(output, base),
  _var(var)
  {}
  