Bug 73729 [Workbench] [Mac] Dual preferences menu items
On Mac OS X, the preferences menu item appears in the Eclipse menu. This is correct. However, the same menu item that does the same thing also appears in the Window menu, which is correct on other platforms but not the Mac. It should be removed from the Window menu.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/WorkbenchActionBuilder.java
* Adds a <code>GroupMarker</code> or <code>Separator</code> to a menu.
	 * The test for whether a separator should be added is done by checking for
	 * the existence of a preference matching the string
	 * useSeparator.MENUID.GROUPID that is set to <code>true</code>.
	 * 
	 * @param menu
	 *            the menu to add to
	 * @param groupId
	 *            the group id for the added separator or group marker
	 */
	private void addSeparatorOrGroupMarker(MenuManager menu, String groupId) {
		String prefId = "useSeparator." + menu.getId() + "." + groupId; 
		boolean addExtraSeparators = IDEWorkbenchPlugin.getDefault()
				.getPreferenceStore().getBoolean(prefId);
		if (addExtraSeparators) {
			menu.add(new Separator(groupId));
		} else {
			menu.add(new GroupMarker(groupId));
		}
	}
    
    /**
     * Disposes any resources and unhooks any listeners that are no longer needed.
     * Called when the window is closed.
     */
    public void dispose() {
        if (isDisposed) {
			return;
		}
    	isDisposed = true;