解决QT5.5.1 could not find or load the Qt platform plugin "windows"

开发版本：qt-opensource-windows-x86-mingw492-5.5.1

安装路径：C:\Qt\Qt5.5.1_mingw

解决方法：

拷贝 C:\Qt\Qt5.5.1_mingw\5.5\mingw492_32\plugins\platforms 目录到exe程序所在目录（由于是Release发布，所有“d.dll”结尾的dll可以忽略不要）

exe所在目录结构参考如下

./Qt5WebKitWidgets.dll
./Qt5WebChannel.dll
./Qt5PrintSupport.dll
./app.exe
./Qt5Gui.dll
./icuuc54.dll
./icuin54.dll
./icudt54.dll
./Qt5Quick.dll
./Qt5Positioning.dll
./Qt5Sensors.dll
./Qt5OpenGL.dll
./Qt5Network.dll
./Qt5WebKit.dll
./Qt5MultimediaWidgets.dll
./libstdc++-6.dll
./platforms
./platforms/qoffscreen.dll
./platforms/qwindows.dll
./platforms/qminimal.dll
./libgcc_s_dw2-1.dll
./Qt5Multimedia.dll
./Qt5Core.dll
./Qt5Qml.dll
./Qt5Widgets.dll
./libwinpthread-1.dll
./Qt5Sql.dll