Bug 54882 [Fonts] Font definition needs a getBold and getItalic
We need to be able to get the bold and italic version of a font for use in progress among other things. This needs to be wiped out when the definition changes. Kim please point me at where to start.
bundles/org.eclipse.jface/src/org/eclipse/jface/resource/FontRegistry.java
*/
	public boolean hasValueFor(String fontKey){
		return stringToFontData.containsKey(fontKey);
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jface.resource.ResourceRegistry#clearCaches()
	 */
	protected void clearCaches() {
		disposeFonts(stringToFont.values().iterator());
		disposeFonts(staleFonts.iterator());
		stringToFont.clear();
		staleFonts.clear();
	}
	
	/**
	 * Dispose of all of the fonts in this iterator.
	 * @param Iterator over Collection of Font
	 */
	private void disposeFonts(Iterator iterator) {
		while (iterator.hasNext()) {
			Object next = iterator.next();
			((Font) next).dispose();
		}
	}
	
	/**
	 * Hook a dispose listener on the SWT display.
	 */
	private void hookDisplayDispose(Display display) {
		display.disposeExec(displayRunnable);