[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/Target/RISCV/RISCVTargetMachine.cpp b/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
index f4e6ed9..c9614cc 100644
--- a/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
+++ b/llvm/lib/Target/RISCV/RISCVTargetMachine.cpp
@@ -58,7 +58,7 @@
     : LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
                         getEffectiveRelocModel(TT, RM),
                         getEffectiveCodeModel(CM, CodeModel::Small), OL),
-      TLOF(make_unique<RISCVELFTargetObjectFile>()),
+      TLOF(std::make_unique<RISCVELFTargetObjectFile>()),
       Subtarget(TT, CPU, FS, Options.MCOptions.getABIName(), *this) {
   initAsmInfo();
 }