[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/lib/Transforms/IPO/WholeProgramDevirt.cpp b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
index 4436363..4490a7e 100644
--- a/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
+++ b/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp
@@ -644,7 +644,7 @@
     // an optimization remark emitter on the fly, when we need it.
     std::unique_ptr<OptimizationRemarkEmitter> ORE;
     auto OREGetter = [&](Function *F) -> OptimizationRemarkEmitter & {
-      ORE = make_unique<OptimizationRemarkEmitter>(F);
+      ORE = std::make_unique<OptimizationRemarkEmitter>(F);
       return *ORE;
     };