support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Shell/Standard/StartupInput.cs

@@ -0,0 +1,15 @@
+namespace Standard
+{
+    using System;
+    using System.Runtime.InteropServices;
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal class StartupInput
+    {
+        public int GdiplusVersion = 1;
+        public IntPtr DebugEventCallback;
+        public bool SuppressBackgroundThread;
+        public bool SuppressExternalCodecs;
+    }
+}
+