Fix #1752: ExpandUsingDeclarations not saved.

ILSpy/Options/DisplaySettingsPanel.xaml.cs

@@ -134,6 +134,7 @@ namespace ICSharpCode.ILSpy.Options
 			section.SetAttributeValue("SortResults", s.SortResults);
 			section.SetAttributeValue("FoldBraces", s.FoldBraces);
 			section.SetAttributeValue("ExpandMemberDefinitions", s.ExpandMemberDefinitions);
+			section.SetAttributeValue("ExpandUsingDeclarations", s.ExpandUsingDeclarations);
 			section.SetAttributeValue("IndentationUseTabs", s.IndentationUseTabs);
 			section.SetAttributeValue("IndentationSize", s.IndentationSize);
 			section.SetAttributeValue("IndentationTabSize", s.IndentationTabSize);