[PATCH v2 3/4] math: Use stdbit.h instead of builtin in math_config.h

[Wilco Dijkstra]

Hi Adhemerval,

Looks fine. Note we need to check whether roundeven is needed for
any math functions - it appears round() will work equally well in most
cases.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

Cheers,
Wilco