Update the release notes about how to enable the loop vectorizer.

llvm-svn: 166123

llvm/docs/ReleaseNotes.html

@@ -467,8 +467,8 @@ Release Notes</a>.</h1>
    includes a few major enhancements and additions to the optimizers:</p>
 
 <p> Loop Vectorizer -  We've added a basic loop vectorizer and we are now able
-    to vectorize small loops. In this release the loop vectorizer is only
-    available using the stand alone command line tools. </p>
+    to vectorize small loops. The loop vectorizer is disabled by default and
+    can be enabled using the -mllvm -vectorize flags. </p>
 
 <ul>
   <li>...</li>