quick-cocos2d-x 2.2.3 rc版本中 crypto.md5file() 的C++实现在ANDROID上有BUG

原来的版本是用fopen打开文件的，如果要从ANDROID的APK中取文件，直接就洗白了
修改如下

void CCCrypto::MD5File(const char* path, unsigned char* output)
{
    unsigned long len = 0;
    //to make sure we can get data of files easily from ios,android,pc etc.
    //we use CCFileUtils::sharedFileUtils()->getFileData
    unsigned char* pData = CCFileUtils::sharedFileUtils()->getFileData(path, "r", &len);
    if (pData == NULL || len == 0){
        CCLOG("CCCrypto::MD5File() can't open file %s", path);
        return;
    }
    
    MD5_CTX ctx;
    MD5_Init(&ctx);

    MD5_Update(&ctx, pData, len);
    MD5_Final(output, &ctx);

    //delete data as CCFileUtils::sharedFileUtils()->getFileData claimed.
    if (pData != NULL)
    delete[] pData;
}