SERVER-6086 linenoise handles backspace incorrectly with Korean character set

 - use mk_wcswidth before refresh line. for calculate width.
How about introducing a static function calculateColumnPositions(buf32, pos) and calling it as you are specifying the parameters to calculateScreenPosition?


```
calculateScreenPosition( xEndOfPrompt, ...,
                         calculateColumnPositions( buf32, pos ),
                         xCursorPos, ... );
```

Also, our code style limits length of each line to 100 characters.