Add safe size_t math APIs

[dthaler]

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[nibanks]

LGTM. General question though: Can/should we move stuff to be header only (via macros or possibly inline functions) instead of functions defined in separate files? Ideally the linker should do a good job of eliminating overhead, but it doesn't always do it perfect.

[dthaler]

LGTM. General question though: Can/should we move stuff to be header only (via macros or possibly inline functions) instead of functions defined in separate files? Ideally the linker should do a good job of eliminating overhead, but it doesn't always do it perfect.

The downside of macros/inlines is that if they're non-trivial and used a lot, then they can increase the footprint and memory requirements. So I would say: yes for trivial functions, no for complex functions. Can do a pass in a separate PR.