Add a blurb about MachineInstr bundling support.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146603 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/ReleaseNotes.html b/docs/ReleaseNotes.html
index 4d2f5c4..b9361a5 100644
--- a/docs/ReleaseNotes.html
+++ b/docs/ReleaseNotes.html
@@ -263,7 +263,10 @@
 <p>LLVM 3.1 includes several major changes and big features:</p>
 
 <ul>
-  <li><a href="../tools/clang/docs/AddressSanitizer.html">AddressSanitizer</a>, a fast memory error detector.</li>
+  <li><a href="../tools/clang/docs/AddressSanitizer.html">AddressSanitizer</a>,
+      a fast memory error detector.</li>
+  <li><a href="CodeGenerator.html#machineinstrbundle">MachineInstr Bundles</a>,
+      Support to model instruction bundling / packing.</li>
   <li>....</li>
 </ul>