[libvirt] how to print size_t in LGPLv2+ program

[Bruno Haible]

> > What a shame that POSIX omitted an <inttypes.h> PRIu* for size_t.
> 
> You can define it by yourself ...

Or use uintptr_t instead of size_t. By the definition of these types,
you can be sure that uintptr_t is at least as wide as size_t. Then use

  printf ("%" PRIuPTR, (uintptr_t) size_t_value);

- Works fine with gnulib's <inttypes.h>.
- Works fine with gettext.
- Doesn't need gettext or glibc versions that don't exist yet.

Bruno