xlib part of bug 243966: getPropertyValue truncates values for computed system font value

patch by Karsten D��sterloh <mnyromyr@tprac.de> r=roland.mainz@nrubsig.org

gfx/src/xlib/nsDeviceContextXlib.cpp

@@ -361,6 +361,8 @@ NS_IMETHODIMP nsDeviceContextXlib::GetSystemFont(nsSystemFontID anID, nsFont *aF
       break;
   }
 
+  aFont->systemFont = PR_TRUE;
+
   return NS_OK;
 }