Add missing uses of PRI constants.
Create a PRI constant for size_t, since %z isn't available on all
platforms. Notably, the legacy Windows runtime needs %I instead of %z.
Use that on UCRT as well, since there doesn't seem to be a way to
determine if you are compiling for MSVCRT or UCRT.
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
595afc6f4b