message: Correctly generate identifier for enums.
  This should allow the EnumName* function to work with enums generated
  using the --scoped-enum flag.
diff: @@ -991,7 +991,7 @@ class CppGenerator : public BaseGenerator {
  for (auto it = enum_def.vals.vec.begin(); it != enum_def.vals.vec.end();
  ++it) {
  const auto &ev = **it;
  - code_ += " case {{ENUM_NAME}}_" + Name(ev) + ": return \"" +
  + code_ += " case " + GetEnumValUse(enum_def, ev) + ": return \"" +
  Name(ev) + "\";";
  }
  