Change FormatFixed to avoid bounds checks
Change FormatFixed to avoid bounds checks

Match the original native code's use of pointers.

mmitche/coreclr,krk/coreclr,wtgodbe/coreclr,wtgodbe/coreclr,wtgodbe/coreclr,yizhang82/coreclr,krk/coreclr,ruben-ayrapetyan/coreclr,wtgodbe/coreclr,cshung/coreclr,mmitche/coreclr,krk/coreclr,yizhang82/coreclr,ruben-ayrapetyan/coreclr,mmitche/coreclr,JosephTremoulet/coreclr,JosephTremoulet/coreclr,yizhang82/coreclr,krk/coreclr,mmitche/coreclr,cshung/coreclr,mmitche/coreclr,JosephTremoulet/coreclr,JosephTremoulet/coreclr,cshung/coreclr,JosephTremoulet/coreclr,ruben-ayrapetyan/coreclr,wtgodbe/coreclr,ruben-ayrapetyan/coreclr,poizan42/coreclr,poizan42/coreclr,ruben-ayrapetyan/coreclr,yizhang82/coreclr,yizhang82/coreclr,mmitche/coreclr,poizan42/coreclr,wtgodbe/coreclr,yizhang82/coreclr,poizan42/coreclr,cshung/coreclr,JosephTremoulet/coreclr,poizan42/coreclr,poizan42/coreclr,krk/coreclr,krk/coreclr,ruben-ayrapetyan/coreclr,cshung/coreclr,cshung/coreclr