Add note about cmake. Patch by Oscar Fuentes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58712 91177308-0d34-0410-b5e6-96231b3b80d8

docs/ReleaseNotes.html

@@ -482,6 +482,10 @@ faster:</p>
     have switched over to use it.   The eventual goal is to eliminate
     std::ostream in favor of it.</li>
 
+<li><p>LLVM 2.4 includes an optional build system based on CMake. It
+    still is on its early stages but can be useful for Visual C++
+    userswho can not use the Visual Studio IDE.</p></li>
+
 </ul>
 
 </div>