SWT typed listener support.

## Package Specification

This package provides the typed events and listener interfaces and, where appropriate, matching adapter classes which make up the "high level" typed listener support provided by SWT.

For contrast, see also the untyped listener support provided by class `org.eclipse.swt.widgets.Event` and interface `org.eclipse.swt.widgets.Listener`, and the `addListener` and `removeListener` methods in class `org.eclipse.swt.widgets.Widget`.