Use std::ostringstream for numeric formatting

[cdunn2001]

We've had lots of problems with std::snprintf. E.g. #418.

As BillyGoto says:

Could we switch to std::ostringstream instead? Its numeric formatting is actually specified in terms of printf's output, and it's everywhere.

[dota17]

I've tried to refactory valueToString(), but I find that it's performance is not very good.
If we consider the performance or efficiency, std::ostringstream() performance is not comparable to std::snprintf(), if we consider the safety or simplicity std::ostringstream() is better than std::snprintf().