fix README title
修正README标题

Signed-off-by: Wanpeng Song <swpustc@mail.ustc.edu.cn>
Upgrade libpng
升级libpng

Signed-off-by: Wanpeng Song <swpustc@mail.ustc.edu.cn>
fix string_printf comment
修正string_printf注释

Signed-off-by: Wanpeng Song <swpustc@mail.ustc.edu.cn>
Update dumpImageSize version to 1.1.9.8
更新dumpImageSize版本到1.1.9.8

Signed-off-by: Wanpeng Song <swpustc@mail.ustc.edu.cn>
Merge branch 'dev-2'

Signed-off-by: Wanpeng Song <swpustc@mail.ustc.edu.cn>