Add a divide rounding up safe math function.

Add a divide rounding up safe math function.

This function takes arguments a & b and computes a / b rounding any
remainder up.

It is safe with respect to overflow and negative inputs.  It's only fast for
non-negative inputs.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/17884)