Update QT to 4.8.6

The current version can't be downloaded any more:
```
Downloading http://download.qt-project.org/official_releases/qt/4.8/4.8.5/qt-everywhere-opensource-src-4.8.5.tar.gz...
[ERROR] urllib failed to download (code: 404): http://download.qt-project.org/official_releases/qt/4.8/4.8.5/qt-everywhere-opensource-src-4.8.5.tar.gz
```
And the new version 5.3.1 doesn't compile with the current build script.