Compress a target into compact "bits": exact port of arith_uint256::GetCompact (round-trips consensus semantics: retarget comparisons happen in compact form, so precision loss here is consensus-correct, not a bug).
Compress a target into compact "bits": exact port of arith_uint256::GetCompact (round-trips consensus semantics: retarget comparisons happen in compact form, so precision loss here is consensus-correct, not a bug).