我刚刚在我的机器上安装了最新版本的 cygwin 和 eclipse luna。它工作正常，我能够运行我的项目。但是，当我构建它们时，我收到了我不明白的警告。例如，这是我从“c++ Primer”一书的网站上获得的头文件“Sales_item.h”的警告:

warning: defaulted and deleted functions only available with -std=c++11 or -std=gnu++11 [enabled by default]
     Sales_item() = default;
                    ^
../src/Sales_item.h:70:27: warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11 [enabled by default]
     unsigned units_sold = 0; // explicitly initialized
                           ^
../src/Sales_item.h:71:22: warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11 [enabled by default]
     double revenue = 0.0;
                      ^
Finished building: ..

这些警告是什么意思？我应该做点什么吗？