[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

llvm/lib/Bitcode/Reader/MetadataLoader.cpp

@@ -2133,7 +2133,7 @@ MetadataLoader::MetadataLoader(BitstreamCursor &Stream, Module &TheModule,
                                BitcodeReaderValueList &ValueList,
                                bool IsImporting,
                                std::function<Type *(unsigned)> getTypeByID)
-    : Pimpl(llvm::make_unique<MetadataLoaderImpl>(
+    : Pimpl(std::make_unique<MetadataLoaderImpl>(
           Stream, TheModule, ValueList, std::move(getTypeByID), IsImporting)) {}
 
 Error MetadataLoader::parseMetadata(bool ModuleLevel) {