Not all platforms on which we compile define PRI[doux]16.

Not all platforms on which we compile define PRI[doux]16.

So don't use it; it's not necessary on any of the platforms on which we
work.  (The *only* ones that are needed are PRI[doux]64, because
sometimes you need %ll[doux], sometimes you need %l[doux], and with MSVC
you need whatever its run-time library requires.)