support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Shell/Standard/SIGDN.cs

@@ -0,0 +1,18 @@
+namespace Standard
+{
+    using System;
+
+    internal enum SIGDN : uint
+    {
+        DESKTOPABSOLUTEEDITING = 0x8004c000,
+        DESKTOPABSOLUTEPARSING = 0x80028000,
+        FILESYSPATH = 0x80058000,
+        NORMALDISPLAY = 0,
+        PARENTRELATIVE = 0x80080001,
+        PARENTRELATIVEEDITING = 0x80031001,
+        PARENTRELATIVEFORADDRESSBAR = 0x8007c001,
+        PARENTRELATIVEPARSING = 0x80018001,
+        URL = 0x80068000
+    }
+}
+