message: Remove unimplemented function
  Looks like this was an unintended sideeffect of r124250.
diff: @@ -147,12 +147,6 @@ Type::Type(const Type &rhs)
  m_byte_size_has_value(rhs.m_byte_size_has_value), m_decl(rhs.m_decl),
  m_compiler_type(rhs.m_compiler_type), m_flags(rhs.m_flags) {}
  -const Type &Type::operator=(const Type &rhs) {
  - if (this != &rhs) {
  - }
  - return *this;
  -}
  -
  void Type::GetDescription(Stream *s, lldb::DescriptionLevel level,
  bool show_name) {
  *s << "id = " << (const UserID &)*this;
  