Bug 57762 [Dialogs] honor the platform button dismissal alignment on Mac and GTK
Button ordering is inverted on these platforms. See Display.getDismissalAlignment() or the equivalent JFace mechansim.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/Dialog.java
*            the number of characters
	 * @return the number of pixels
	 * @since 2.0
	 */
	public static int convertHeightInCharsToPixels(FontMetrics fontMetrics,
			int chars) {
		return fontMetrics.getHeight() * chars;
	}
	/**
	 * Returns the number of pixels corresponding to the given number of
	 * horizontal dialog units.
	 * <p>
	 * The required <code>FontMetrics</code> parameter may be created in the
	 * following way: <code>
	 * 	GC gc = new GC(control);
	 *	gc.setFont(control.getFont());
	 *	fontMetrics = gc.getFontMetrics();
	 *	gc.dispose();
	 * </code>
	 * </p>
	 * 
	 * @param fontMetrics
	 *            used in performing the conversion
	 * @param dlus
	 *            the number of horizontal dialog units
	 * @return the number of pixels
	 * @since 2.0
	 */
	public static int convertHorizontalDLUsToPixels(FontMetrics fontMetrics,
			int dlus) {