tools/nolibc: ensure fast64 integer types have 64 bits

On 32bit platforms size_t is not enough to represent [u]int_fast64_t.

Fixes: 3e9fd4e9 ("tools/nolibc: add integer types and integer limit macros")
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>