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 (list.size() == 1) {
			return true;
		}
		return false;
	}
	private boolean canRemove(List list) { 
		return !list.isEmpty();
	}
	private CPListElement[] openExtJarFileDialog(CPListElement existing, Object parent) {
		String lastUsedPath;
		if (existing != null) {
			lastUsedPath= existing.getPath().removeLastSegments(1).toOSString();
		} else {
			lastUsedPath= fDialogSettings.get(IUIConstants.DIALOGSTORE_LASTEXTJAR);
			if (lastUsedPath == null) {
				lastUsedPath= ""; 
			}
		}
		String title= (existing == null) ? PreferencesMessages.getString("UserLibraryPreferencePage.browsejar.new.title") : PreferencesMessages.getString("UserLibraryPreferencePage.browsejar.edit.title"); 
		
		FileDialog dialog= new FileDialog(getShell(), existing == null ? SWT.MULTI : SWT.SINGLE);
		dialog.setText(title);
		dialog.setFilterExtensions(new String[] {"*.jar;*.zip"}); 
		dialog.setFilterPath(lastUsedPath);
		if (existing != null) {
			dialog.setFileName(existing.getPath().lastSegment());
		}
		
		String res= dialog.open();
		if (res == null) {