support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Shell/Standard/NIIF.cs

@@ -0,0 +1,18 @@
+namespace Standard
+{
+    using System;
+
+    internal enum NIIF
+    {
+        ERROR = 3,
+        INFO = 1,
+        LARGE_ICON = 0x20,
+        NIIF_RESPECT_QUIET_TIME = 0x80,
+        NONE = 0,
+        NOSOUND = 0x10,
+        USER = 4,
+        WARNING = 2,
+        XP_ICON_MASK = 15
+    }
+}
+