[AsmPrinter] Make AsmPrinter's OutStreamer member a unique_ptr.

AsmPrinter owns the OutStreamer, so an owning pointer makes sense here. Using a
reference for this is crufty.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235752 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/AsmPrinter.h

@@ -78,7 +78,7 @@ public:
   /// This is the MCStreamer object for the file we are generating. This
   /// contains the transient state for the current translation unit that we are
   /// generating (such as the current section etc).
-  MCStreamer &OutStreamer;
+  std::unique_ptr<MCStreamer> OutStreamer;
 
   /// The current machine function.
   const MachineFunction *MF;