[llvm] Migrate llvm::make_unique to std::make_unique

Now that we've moved to C++14, we no longer need the llvm::make_unique
implementation from STLExtras.h. This patch is a mechanical replacement
of (hopefully) all the llvm::make_unique instances across the monorepo.

llvm-svn: 369013
diff --git a/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl07.rst b/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl07.rst
index 8013dec..218e441 100644
--- a/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl07.rst
+++ b/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl07.rst
@@ -780,7 +780,7 @@
       if (!Body)
         return nullptr;
 
-      return llvm::make_unique<VarExprAST>(std::move(VarNames),
+      return std::make_unique<VarExprAST>(std::move(VarNames),
                                            std::move(Body));
     }