我在vs2010上调试，调用了setstring方法
用内存泄露检查发现会有
很多的类似 e:cocos2d-x-stoneagecocos2dxlabel_nodescclabelbmfont.cpp(324) : {12598} normal block at 0x0A9CFF78, 4 bytes long.
Data: <0 > 30 00 00 00
指向CCLabelBMF中的324行unsigned short* str_new = new unsigned short;