This check puts all of our code in a C++ anonymous namespace, which is
effectively making all functions `static`. This allows the compiler to
determine that a function is unused, so we can delete it.
We put some tokstyle exemptions into the source files themselves,
instead. This way we can check some of the code in those files, and more
in the future when tokstyle supports more constructs (like apidsl).
Also: hacked ping_array.api.h to not emit `_array` as parameter names.
We'll need to fix apidsl to do this better. This works for now.
