[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/ExecutionEngine/Orc/ExecutionUtils.cpp b/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
index 044e7ee..990fc13 100644
--- a/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
+++ b/llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp
@@ -186,7 +186,7 @@
   auto Lib = sys::DynamicLibrary::getPermanentLibrary(FileName, &ErrMsg);
   if (!Lib.isValid())
     return make_error<StringError>(std::move(ErrMsg), inconvertibleErrorCode());
-  return llvm::make_unique<DynamicLibrarySearchGenerator>(
+  return std::make_unique<DynamicLibrarySearchGenerator>(
       std::move(Lib), GlobalPrefix, std::move(Allow));
 }