+ We have been told that the meid will be a string, so we enforce that even if
+ the user is copying in bytes. We will add a 0 byte at len+1 when len is less
+ than the field size, or as the last byte (doing damage to their string) if
+ the caller didn't play by the rules. If they pass a non-nil terminated set
+ of bytes which are the field length, we'll indicate truncation.
+