Should use desktop settings instead of hardcoded constants

Starting with the fix for 6176814, a double click is recognized on XAWT
only if the distance between 2 successive mouse presses is not greater
than the constant 4. A desktop property (see Toolkit.getDesktopProperty())
should be used intead of the constant. On X platforms the desktop property
should be mapped to XSETTING Net/DoubleClickDistance (refer to
http://freedesktop.org/wiki/Standards_2fXSettingsRegistry).

There may be other places in AWT where desktop settings should be used
instead of hardcoded contants.

###@###.### 2004-12-23 15:24:02 GMT