support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Shell/Standard/SHCONTF.cs

@@ -0,0 +1,21 @@
+namespace Standard
+{
+    using System;
+
+    internal enum SHCONTF
+    {
+        CHECKING_FOR_CHILDREN = 0x10,
+        ENABLE_ASYNC = 0x8000,
+        FASTITEMS = 0x2000,
+        FLATLIST = 0x4000,
+        FOLDERS = 0x20,
+        INCLUDEHIDDEN = 0x80,
+        INIT_ON_FIRST_NEXT = 0x100,
+        NAVIGATION_ENUM = 0x1000,
+        NETPRINTERSRCH = 0x200,
+        NONFOLDERS = 0x40,
+        SHAREABLE = 0x400,
+        STORAGE = 0x800
+    }
+}
+