Add a note about improved alignment detection.

llvm-svn: 52009
diff --git a/llvm/docs/ReleaseNotes.html b/llvm/docs/ReleaseNotes.html
index 9222009..564c759 100644
--- a/llvm/docs/ReleaseNotes.html
+++ b/llvm/docs/ReleaseNotes.html
@@ -225,6 +225,8 @@
 memcpy calls, unneeded copies of aggregates, and handles the return slot
 optimization.  The LLVM optimizer now notices long sequences of consequtive
 stores and merges them into memcpy's where profitable.</li>
+<li>Alignment detection for vector memory references and for memcpy and
+memset is now more aggressive.</li> 
 </ul>
 
 </div>