[RFC][PATCH 00/13] Provide saturating helpers for allocation

[Kees Cook]

This is a stab at providing three new helpers for allocation size
calculation:

struct_size(), array_size(), and array3_size().

These are implemented on top of Rasmus's overflow checking functions,
and the last 8 patches are all treewide conversions of open-coded
multiplications into the various combinations of the helper functions.

-Kees