Bug 37917 Compiler prefs - shouldn't complain about wrong source level when resetting defaults [build path]
Build R2.1 Open workspace compiler compliance preferences. By default, these point at 1.3 compliance level, with default compliance settings. Now, switch to 1.4. Observe that default settings are updated (ok). Uncheck the default checkbox, and switch general compliance back to 1.3. Observe that it complains about source level issue (ok). Recheck the use default settings, which will change source level to 1.3 default, and observe that the complaint about source level is still shown !?!
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/CompilerConfigurationBlock.java
group.setText(PreferencesMessages.getString("CompilerConfigurationBlock.classfiles.group.label")); 
		group.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
		group.setLayout(layout);
		String[] generateValues= new String[] { GENERATE, DO_NOT_GENERATE };
		label= PreferencesMessages.getString("CompilerConfigurationBlock.variable_attr.label"); 
		addCheckBox(group, label, PREF_LOCAL_VARIABLE_ATTR, generateValues, 0);
		
		label= PreferencesMessages.getString("CompilerConfigurationBlock.line_number_attr.label"); 
		addCheckBox(group, label, PREF_LINE_NUMBER_ATTR, generateValues, 0);		
		label= PreferencesMessages.getString("CompilerConfigurationBlock.source_file_attr.label"); 
		addCheckBox(group, label, PREF_SOURCE_FILE_ATTR, generateValues, 0);		
		label= PreferencesMessages.getString("CompilerConfigurationBlock.codegen_unused_local.label"); 
		addCheckBox(group, label, PREF_CODEGEN_UNUSED_LOCAL, new String[] { PRESERVE, OPTIMIZE_OUT }, 0);	
		
		return compComposite;
	}
		
	
	/* (non-javadoc)
	 * Update fields and validate.
	 * @param changedKey Key that changed, or null, if all changed.
	 */	
	protected void validateSettings(String changedKey, String newValue) {
		if (changedKey != null) {
			if (INTR_DEFAULT_COMPLIANCE.equals(changedKey)) {
				updateComplianceEnableState();
				if (DEFAULT.equals(newValue)) {
					updateComplianceDefaultSettings();
				}
			} else if (PREF_COMPLIANCE.equals(changedKey)) {