support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Shell/Standard/NIF.cs

@@ -0,0 +1,20 @@
+namespace Standard
+{
+    using System;
+
+    [Flags]
+    internal enum NIF : uint
+    {
+        GUID = 0x20,
+        ICON = 2,
+        INFO = 0x10,
+        MESSAGE = 1,
+        REALTIME = 0x40,
+        SHOWTIP = 0x80,
+        STATE = 8,
+        TIP = 4,
+        VISTA_MASK = 0xfb,
+        XP_MASK = 0x3b
+    }
+}
+