Update: Use F_utf_not instead of F_utf and other resulting changes.

Update: Use F_utf_not instead of F_utf and other resulting changes.

The F_utf_not is semantically more correct than F_utf when returning an error for an invalid UTF-8 sequence.
Use F_utf_fragment where appropriate as well.

Updating all of the appropriate comments revealed some documentation and code structure problems in the fss projects.
These are cleaned up as well.