Cleaning up some XML docs.

Ix.NET/Source/System.Interactive/System/Linq/IAwaitable.cs

@@ -4,8 +4,15 @@
 
 namespace System.Linq
 {
+    /// <summary>
+    /// Interface for objects that can be awaited for the completion of an asynchronous operation.
+    /// </summary>
     public interface IAwaitable
     {
+        /// <summary>
+        /// Gets an awaiter object.
+        /// </summary>
+        /// <returns>Awaiter object.</returns>
         IAwaiter GetAwaiter();
     }
 }

Ix.NET/Source/System.Interactive/System/Linq/IAwaiter.cs

@@ -6,9 +6,23 @@ using System.Runtime.CompilerServices;
 
 namespace System.Linq
 {
+    /// <summary>
+    /// Interface for an awaiter of an asynchronous operation.
+    /// </summary>
     public interface IAwaiter : ICriticalNotifyCompletion
     {
+        /// <summary>
+        /// Gets a Boolean value indicating whether the asynchronous operation has completed.
+        /// </summary>
         bool IsCompleted { get; }
+
+        /// <summary>
+        /// Gets the result of the asynchronous operation.
+        /// </summary>
+        /// <remarks>
+        /// This method may cause blocking if invoked prior to <see cref="IsCompleted"/> returning <c>true</c>.
+        /// Completion of the asynchronous operation can be observed using <see cref="INotifyCompletion.OnCompleted(Action)"/>.
+        /// </remarks>
         void GetResult();
     }
 }

Ix.NET/Source/System.Interactive/System/Linq/IYielder.cs

@@ -2,24 +2,22 @@
 // The .NET Foundation licenses this file to you under the Apache 2.0 License.
 // See the LICENSE file in the project root for more information. 
 
-using System.Security;
-
 namespace System.Linq
 {
     /// <summary>
-    ///     Interface for yielding elements to enumerator.
+    /// Interface for yielding elements to enumerator.
     /// </summary>
     /// <typeparam name="T">Type of the elements yielded to an enumerator.</typeparam>
     public interface IYielder<in T>
     {
         /// <summary>
-        ///     Stops the enumeration.
+        /// Stops the enumeration.
         /// </summary>
         /// <returns>Awaitable object for use in an asynchronous method.</returns>
         IAwaitable Break();
 
         /// <summary>
-        ///     Yields a value to the enumerator.
+        /// Yields a value to the enumerator.
         /// </summary>
         /// <param name="value">Value to yield return.</param>
         /// <returns>Awaitable object for use in an asynchronous method.</returns>