Bug 61713 MessageDialog can't be created in non UI thread anymore
I20040511 In the past it was possible to create a MessageDialog from non UI threads. This is not possible with I20040511 anymore. Doing so now results in an invalid thread access to due the fact that the images are now managed by SWT.
bundles/org.eclipse.jface/src/org/eclipse/jface/resource/ImageRegistry.java
for (Iterator e = table.values().iterator(); e.hasNext();) {
			Entry entry = (Entry) e.next();
			if (entry.image != null) {
				entry.image.dispose();
			}
		}
		table = null;
	}
	/**
	 * Hook a dispose listener on the SWT display.
	 *
	 * @param display the Display
	 */
	private void hookDisplayDispose(Display display) {
		display.disposeExec(new Runnable() {
			public void run() {
				handleDisplayDispose();
			}
		});
	}
	/**
	 * Adds (or replaces) an image descriptor to this registry. The first time
	 * this new entry is retrieved, the image descriptor's image will be computed 
	 * (via </code>ImageDescriptor.createImage</code>) and remembered. 
	 * This method replaces an existing image descriptor associated with the 
	 * given key, but fails if there is a real image associated with it.
	 *
	 * @param key the key
	 * @param descriptor the ImageDescriptor
	 * @exception IllegalArgumentException if the key already exists