Decode a lower-case bytewords string in style, verifying and stripping
the CRC-32. Case-sensitive, as the reference's bytewords::decode; the
single-part UR parser lower-cases a whole UR string before reaching here.
Bytewords for non-ASCII input, an odd-length minimal
string, an unknown word (an upper-case letter makes one), or a checksum
mismatch, checked in that order.
Decode a lower-case bytewords string in
style, verifying and stripping the CRC-32. Case-sensitive, as the reference'sbytewords::decode; the single-part UR parser lower-cases a whole UR string before reaching here.