[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/DebugInfo/PDB/PDBSymbolFunc.cpp b/llvm/lib/DebugInfo/PDB/PDBSymbolFunc.cpp
index 7c3ba98..cb0329b 100644
--- a/llvm/lib/DebugInfo/PDB/PDBSymbolFunc.cpp
+++ b/llvm/lib/DebugInfo/PDB/PDBSymbolFunc.cpp
@@ -79,7 +79,7 @@
 
 std::unique_ptr<IPDBEnumChildren<PDBSymbolData>>
 PDBSymbolFunc::getArguments() const {
-  return llvm::make_unique<FunctionArgEnumerator>(Session, *this);
+  return std::make_unique<FunctionArgEnumerator>(Session, *this);
 }
 
 void PDBSymbolFunc::dump(PDBSymDumper &Dumper) const { Dumper.dump(*this); }