Bug 63840 warning on unused labels
we have warnings for all sorts of unused things. one for unused labels would be good too.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/ProblemSeveritiesConfigurationBlock.java
label= PreferencesMessages.ProblemSeveritiesConfigurationBlock_pb_unused_private_label; 
		addComboBox(inner, label, PREF_PB_UNUSED_PRIVATE, errorWarningIgnore, errorWarningIgnoreLabels, defaultIndent);
		
		label= PreferencesMessages.ProblemSeveritiesConfigurationBlock_pb_unnecessary_else_label; 
		addComboBox(inner, label, PREF_PB_UNNECESSARY_ELSE, errorWarningIgnore, errorWarningIgnoreLabels, defaultIndent);
		
		label= PreferencesMessages.ProblemSeveritiesConfigurationBlock_pb_unnecessary_type_check_label; 
		addComboBox(inner, label, PREF_PB_UNNECESSARY_TYPE_CHECK, errorWarningIgnore, errorWarningIgnoreLabels, defaultIndent);
		
		label= PreferencesMessages.ProblemSeveritiesConfigurationBlock_pb_unused_throwing_exception_label; 
		addComboBox(inner, label, PREF_PB_UNUSED_DECLARED_THROWN_EXCEPTION, errorWarningIgnore, errorWarningIgnoreLabels, defaultIndent);
		
		label= PreferencesMessages.ProblemSeveritiesConfigurationBlock_pb_unused_throwing_exception_when_overriding_label; 
		addCheckBox(inner, label, PREF_PB_UNUSED_DECLARED_THROWN_EXCEPTION_WHEN_OVERRIDING, enabledDisabled, extraIndent);
		
		
		label= PreferencesMessages.ProblemSeveritiesConfigurationBlock_section_jdk50; 
		excomposite= createStyleSection(composite, label, nColumns);
		
		inner= new Composite(excomposite, SWT.NONE);
		inner.setFont(composite.getFont());
		inner.setLayout(new GridLayout(nColumns, false));
		excomposite.setClient(inner);
		
		label= PreferencesMessages.ProblemSeveritiesConfigurationBlock_pb_unsafe_type_op_label; 
		addComboBox(inner, label, PREF_15_PB_UNCHECKED_TYPE_OPERATION, errorWarningIgnore, errorWarningIgnoreLabels, defaultIndent);
		label= PreferencesMessages.ProblemSeveritiesConfigurationBlock_pb_raw_type_reference; 
		addComboBox(inner, label, PREF_15_PB_RAW_TYPE_REFERENCE, errorWarningIgnore, errorWarningIgnoreLabels, defaultIndent);
		
		label= PreferencesMessages.ProblemSeveritiesConfigurationBlock_pb_final_param_bound_label;