clang-modernize: Tweak docs after rename

* Removing sphinx warnings about docs not in a toctree.
* Adding more links to cpp11-migrate redirect docs.

llvm-svn: 190195
diff --git a/clang-tools-extra/docs/cpp11-migrate.rst b/clang-tools-extra/docs/cpp11-migrate.rst
index 09ee2fd..6854535 100644
--- a/clang-tools-extra/docs/cpp11-migrate.rst
+++ b/clang-tools-extra/docs/cpp11-migrate.rst
@@ -1,7 +1,5 @@
-.. index:: clang-modernize
-
 ============================
 C++11 Migrator User's Manual
 ============================
 
-This tool has been renamed :program:`clang-modernize`.
+This tool has been renamed :doc:`clang-modernize <clang-modernize>`.