Add BindingsNotRewrittenException

src/OpenTK/Exceptions.cs

@@ -47,4 +47,15 @@ namespace OpenTK
         /// </summary>
         public override string Message { get; }
     }
+
+    /// <summary>
+    /// This exception is thown when a binding method is called and the bindings have not been rewritten by Rewrite.exe.
+    /// </summary>
+    public class BindingsNotRewrittenException : Exception
+    {
+        /// <summary>
+        /// Constructs a new BindingsNotRewrittenException instance.
+        /// </summary>
+        public BindingsNotRewrittenException() : base("Rewrite.exe has not been run.") { }
+    }
 }