Construct the MCStreamer before constructing the MCTargetStreamer.

This has a few advantages:
* Only targets that use a MCTargetStreamer have to worry about it.
* There is never a MCTargetStreamer without a MCStreamer, so we can use a
  reference.
* A MCTargetStreamer can talk to the MCStreamer in its constructor.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200129 91177308-0d34-0410-b5e6-96231b3b80d8

lib/MC/MCMachOStreamer.cpp

@@ -38,7 +38,7 @@ private:
 public:
   MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB, raw_ostream &OS,
                   MCCodeEmitter *Emitter)
-      : MCObjectStreamer(Context, 0, MAB, OS, Emitter) {}
+      : MCObjectStreamer(Context, MAB, OS, Emitter) {}
 
   /// @name MCStreamer Interface
   /// @{