This will cause ACK libc to provide int64_t as long (instead of long
long) on LP64, if we ever get such a platform.
LP64 would have 64-bit long and 64-bit long long, so int64_t might be
either type. For example on amd64, int64_t is long in NetBSD libc,
and long long in OpenBSD libc. Support for long long in ACK remains
incomplete (no printf "%lld"), so it seems better to prefer long where
possible. Also, int64_t being long before long long is more
consistent with int32_t being int before long.
Put suffixes on the values of INT32_MAX, INT64_MAX, and related
constants, so they have the same types as int32_t and int64_t.
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