SERVER-6086 linenoise handles backspace incorrectly with Korean character set

 - use mk_wcswidth before refresh line. for calculate width.
right. I agree. just like below.

```
static int calculateColumnPosition( unsigned int* buf32, size_t n) {
    int width = mk_wcswidth( reinterpret_cast<const int*>( buf32 ), n );
    if ( width == -1 )
        return n;
    else
        return width;
}
```