[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/LangImpl05.rst b/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl05.rst
index 685e5fb..0e61c07 100644
--- a/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl05.rst
+++ b/llvm/docs/tutorial/MyFirstLanguageFrontend/LangImpl05.rst
@@ -146,7 +146,7 @@
       if (!Else)
         return nullptr;
 
-      return llvm::make_unique<IfExprAST>(std::move(Cond), std::move(Then),
+      return std::make_unique<IfExprAST>(std::move(Cond), std::move(Then),
                                           std::move(Else));
     }
 
@@ -560,7 +560,7 @@
       if (!Body)
         return nullptr;
 
-      return llvm::make_unique<ForExprAST>(IdName, std::move(Start),
+      return std::make_unique<ForExprAST>(IdName, std::move(Start),
                                            std::move(End), std::move(Step),
                                            std::move(Body));
     }