Reduce minimum bottom border size to look proportional to sides when size >= Normal.

Bottom corner rounding is unaffected.

svn path=/branches/KDE/4.3/kdebase/workspace/; revision=1008903

clients/oxygen/oxygenclient.cpp

@@ -143,7 +143,7 @@ int OxygenClient::layoutMetric(LayoutMetric lm, bool respectWindowState, const K
                 // Even for thin borders (2px wide) we want to preserve
                 // the rounded corners having a minimum height of 7px
                 if (lm == LM_BorderBottom) {
-                    return qMax(frameWidth, 7);
+                    return qMax(frameWidth, 4);
                 } else {
                     return frameWidth;
                 }