fix bugs - potential memory leak.

const std::string text = std::string((char*)ch,0,len); is using next
string constructor.
string (const string& str, size_t pos, size_t len = npos);
memory leak can occur while type converting char to string.

So we have to use next string constructor.
string (const char* s, size_t n);

http://www.cplusplus.com/reference/string/string/string/
Merge pull request #9124 from ricardoquesada/compiler_warnings

fixes compiler warnings
[AUTO][ci skip]: updating cocos2dx_files.json
Merge pull request #9125 from CocosRobot/update_cocosfiles_1415999444

[AUTO][ci skip]: updating cocos2dx_files.json
Merge pull request #9085 from jicheol-ryu/v3

fix bug - potential memory leak.