msvcrt: Fix inconsistent rounding behaviour for sprintf and add tests.

[YongHao Hu]

Thank you for your review and advice. I will try to improve it. :)
By the way, I will send another independent patch to msvcp tests.

On 2015年01月27日 19:02, Piotr Caban wrote:
> This is not correct, val may loose to much precision. Also temp can 
> become INF (in your patch temp is int but I guess it's a mistake). I'm 
> afraid that in order to fix this bug you'll need to stop using glibcs 
> sprintf in wine's printf implementation.
>
> Your patch to msvcp tests depends on this patch. Please send patches 
> that depend on each other in series.