Truncate argument values in CallStackPad.

This avoids performance problems when long strings are passed as arguments.

src/AddIns/Debugger/Debugger.AddIn/Pads/CallStackPad.xaml.cs

@@ -187,6 +187,8 @@ namespace ICSharpCode.SharpDevelop.Gui.Pads
 					if (showArgumentValues) {
 						try {
 							argValue = frame.GetArgumentValue(i).AsString;
+							if (argValue != null && argValue.Length > 100)
+								argValue = argValue.Substring(0, 100) + "...";
 						} catch { }
 					}
 					if (parameterName != null && argValue != null) {