support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Shell/Standard/HCF.cs

@@ -0,0 +1,17 @@
+namespace Standard
+{
+    using System;
+
+    [Flags]
+    internal enum HCF
+    {
+        AVAILABLE = 2,
+        CONFIRMHOTKEY = 8,
+        HIGHCONTRASTON = 1,
+        HOTKEYACTIVE = 4,
+        HOTKEYAVAILABLE = 0x40,
+        HOTKEYSOUND = 0x10,
+        INDICATOR = 0x20
+    }
+}
+