Screen to tile coord

Nobody has claimed this yet.

Just to let you know there is a bug in the ISO conversion from screen to tile.

Found this while debugging my own stuff and comparing to tile.

``` c++
QPointF IsometricRenderer::tileToScreenCoords(qreal x, qreal y) const
{
const int tileWidth = map()->tileWidth();
const int tileHeight = map()->tileHeight();
const int originX = map()->height() * tileWidth / 2;

return QPointF((x - y) * tileWidth / 2 + originX,
(x + y) * tileHeight / 2);
}
```

Actually working with pure int here loses the conversion. (3.9 is rounded to 3 instead of 4....)

In swift, I had to round before converting to Int. Similar fix should work for Tiled.
return ( Int(round(tileY + tileX)), Int(round(tileY - tileX)))

Pretty late, so sorry for the quick and dirty report.

Start at IsometricRenderer::tileToScreenCoords and inspect how the calculated coordinates are converted to integers. Compare the behavior with the reported Swift rounding example; done means fractional results are rounded rather than truncated and screen-to-tile conversion returns the expected tile coordinates.

Written by the indexing model from the issue text.