[libvirt] detecting uses of "%zu"

[Bruno Haible]

Eric Blake wrote:
> it still requires auditing code
> and forbidding "%zu" in favor of "%"PRIuSIZE (or whatever other name we
> settle on).

You could hack GCC, clang, or even xgettext to produce a warning when it
sees a 'z' size modifier in a format string.

Bruno