Update docs to drop support for VS 2008.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186961 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 88c1c05..4b71543 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -54,6 +54,10 @@
   has been integrated into the instruction combiner and function attribute
   marking passes.
 
+* Support for building using Visual Studio 2008 has been dropped. Use VS 2010
+  or later instead. For more information, see the `Getting Started using Visual
+  Studio <GettingStartedVS.html>` page).
+
 * ... next change ...
 
 .. NOTE