|ok||Conversion completed successfully|
|partial||Not all source characters were converted in their entirety.|
This value is returned by member functions in and out if some of the characters in the range could not be converted.
If returned by function member unshift, indicates that the first argument was not a valid state value.
|noconv||For in and out: No conversion needed: source copied.|
For unshift: No termination was needed for this state.