Bugfix: Currency symbols are incorrectly being designated as unassigned.

Bugfix: Currency symbols are incorrectly being designated as unassigned.

An improper check in `private_f_utf_character_is_unassigned()` is resulting in valid currency symbols being treated as undefined.

Example:
```
  # echo "₿" | byte_dump -wt 4
  Piped Byte Dump: (in Hexidecimal)
  0000000000000000  e2 82 bf 0a  | �     ␊  |

  Invalid UTF-8 codes were detected for file '-'.
```

The following is the expected valid results:
```
  # echo "₿" | byte_dump -wt 4
  Piped Byte Dump: (in Hexidecimal)
  0000000000000000  e2 82 bf 0a  | ₿     ␊  |
```