%zu: use SIZE_FMT_SPECIFIER instead

[vtorri]

the purpose of SIZE_FMT_SPECIFIER is to give a crossplatform specifier of %zu, so what about using it ?

note also that in client.c,

libpkgconf/queue.c:             PKGCONF_TRACE(client, "slot %zu: dep %s matched to %p<%s> hits %lu", i, dep->package, dep->match, dep->match->id, dep->match->hits);

last format specifier should be a %zu, not %lu

[vtorri]

i can provide a PR if you want

[Ariadne Conill]

Fixed in 99bc93f