Package-level declarations

Minimal pure-Kotlin unsigned big integer, base 2^32 (limbs are UInt stored in an IntArray little-endian: limb 0 is least significant). Non-negative values only. That is all KiteTorrent's crypto stack needs (MSE Diffie-Hellman modular exponentiation over a fixed 768-bit prime, and the ed25519 field/scalar arithmetic).