message: [Symbol] Remove unused fields from ClangASTContext
diff: @@ -982,7 +982,6 @@ protected:
  std::unique_ptr<clang::ASTContext> m_ast_up;
  std::unique_ptr<clang::LangOptions> m_language_options_up;
  std::unique_ptr<clang::FileManager> m_file_manager_up;
  - std::unique_ptr<clang::FileSystemOptions> m_file_system_options_up;
  std::unique_ptr<clang::SourceManager> m_source_manager_up;
  std::unique_ptr<clang::DiagnosticsEngine> m_diagnostics_engine_up;
  std::unique_ptr<clang::DiagnosticConsumer> m_diagnostic_consumer_up;
  @@ -1001,7 +1000,6 @@ protected:
  clang::ExternalASTMerger::OriginMap m_origins;
  uint32_t m_pointer_byte_size;
  bool m_ast_owned;
  - bool m_can_evaluate_expressions;
  /// The sema associated that is currently used to build this ASTContext.
  /// May be null if we are already done parsing this ASTContext or the
  /// ASTContext wasn't created by parsing source code.
  