[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/tools/llvm-dis/llvm-dis.cpp b/llvm/tools/llvm-dis/llvm-dis.cpp
index 1db498f..ae32951 100644
--- a/llvm/tools/llvm-dis/llvm-dis.cpp
+++ b/llvm/tools/llvm-dis/llvm-dis.cpp
@@ -153,7 +153,7 @@
 
   LLVMContext Context;
   Context.setDiagnosticHandler(
-      llvm::make_unique<LLVMDisDiagnosticHandler>(argv[0]));
+      std::make_unique<LLVMDisDiagnosticHandler>(argv[0]));
   cl::ParseCommandLineOptions(argc, argv, "llvm .bc -> .ll disassembler\n");
 
   std::unique_ptr<MemoryBuffer> MB =