fix finding of datadirectory

Q_WS_X11 isn't defined any longer. Thanks to the Toscano family for the
heads up.

This also fixes locating translations.
Raster is the default graphics system, so no need to specifically set it
Let the style handle the visibility of icons
Set window role regardless of windowing systems. On some systems, it is does nothing
Show icons regardless of windowing system. Also cut off qt versions earlier than 4.6. Even Debian stable has 4.8.