Since Clang enables a couple of warnings that we don't have in GCC,
these were not caught before. Included fixes:
- Use correct printf format string for `size_t`
- Don't compare Nonnull(Ref|Own)Ptr` to nullptr
- Fix unsigned int& => unsigned long& conversion
Problem:
- `static` variables consume memory and sometimes are less
optimizable.
- `static const` variables can be `constexpr`, usually.
- `static` function-local variables require an initialization check
every time the function is run.
Solution:
- If a global `static` variable is only used in a single function then
move it into the function and make it non-`static` and `constexpr`.
- Make all global `static` variables `constexpr` instead of `const`.
- Change function-local `static const[expr]` variables to be just
`constexpr`.
With the goal of centralizing all tests in the system, this is a
first step to establish a Tests sub-tree. It will contain all of
the unit tests and test harnesses for the various components in the
system.
