Bug 55884 Loading a user library from file does not warn when overwriting an existing library [build path]
Works in I2004032400010 + plug-in export for I200403240800 Add library 'mylib'. Save it. Change it. Load library from file. ==> should warn that 'mylib' gets changed.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/UserLibraryPreferencePage.java
if (event.character == SWT.DEL && event.stateMask == 0) {
			List selection= field.getSelectedElements();
			if (canRemove(selection)) {
				doRemove(selection);
			}
		}
	}
	
	private void doEdit(List selected) {
		if (selected.size() == 1) {
			Object curr= selected.get(0);
			if (curr instanceof CPListElementAttribute) {
				editAttributeEntry((CPListElementAttribute) curr);
			} else if (curr instanceof CPUserLibraryElement) {
				editUserLibraryElement((CPUserLibraryElement) curr);
			} else if (curr instanceof CPListElement) {
				CPListElement elem= (CPListElement) curr;
				openExtJarFileDialog(elem, elem.getParentContainer());
			}
		}
	}
	private void editUserLibraryElement(CPUserLibraryElement element) {
		LibraryNameDialog dialog= new LibraryNameDialog(getShell(), element, fLibraryList.getElements());
		if (dialog.open() == Window.OK) {
			CPUserLibraryElement newLibrary= dialog.getNewLibrary();
			if (element != null) {
				fLibraryList.replaceElement(element, newLibrary);
			} else {
				fLibraryList.addElement(newLibrary);
			}