[Clang] 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.

Differential revision: https://reviews.llvm.org/D66259

llvm-svn: 368942
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index 101a135..e8bad88 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -181,7 +181,7 @@
   InitDataSharingAttributesStack();
 
   std::unique_ptr<sema::SemaPPCallbacks> Callbacks =
-      llvm::make_unique<sema::SemaPPCallbacks>();
+      std::make_unique<sema::SemaPPCallbacks>();
   SemaPPCallbackHandler = Callbacks.get();
   PP.addPPCallbacks(std::move(Callbacks));
   SemaPPCallbackHandler->set(*this);