Bug 73083 [Encoding] Need to verify encodings and indicate unavailable ones
When the encodings are set up we need to ensure that they are in the list of valid encodings available from the VM. Those that are not should be indicated as such and not be selectable in the UI.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/ide/dialogs/AbstractEncodingFieldEditor.java
data = new GridData();
		data.horizontalSpan = 2;
		defaultEncodingButton.setLayoutData(data);
		defaultEncodingButton.addSelectionListener(buttonListener);
		defaultEncodingButton.setFont(font);
		otherEncodingButton = new Button(group, SWT.RADIO);
		otherEncodingButton.setText(IDEWorkbenchMessages
				.getString("WorkbenchPreference.otherEncoding")); 
		otherEncodingButton.addSelectionListener(buttonListener);
		otherEncodingButton.setFont(font);
		encodingCombo = new Combo(group, SWT.NONE);
		data = new GridData();
		encodingCombo.setFont(font);
		encodingCombo.setLayoutData(data);
		encodingCombo.addModifyListener(new ModifyListener() {
			public void modifyText(ModifyEvent e) {
				updateValidState();
			}
		});
		return group;
	}
	/**
	 * Get the default encoding for the object being shown.
	 * @return String
	 */
	protected String findDefaultEncoding() {
		return WorkbenchEncoding.getWorkbenchDefaultEncoding();
	}
	/**
	 * Return the text for the default encoding button.