Give the MCStreamer class hierarchy LLVM RTTI facilities for use with
isa<> and dyn_cast<>. In several places, code is already hacking around
the absence of this, and there seem to be several interfaces that might
be lifted and/or devirtualized using this.

This change was based on a discussion with Jim Grosbach about how best
to handle testing for specific MCStreamer subclasses. He said that this
was the correct end state, and everything else was too hacky so
I decided to just make it so.

No functionality should be changed here, this is just threading the kind
through all the constructors and setting up the classof overloads.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174113 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCPureStreamer.cpp b/lib/MC/MCPureStreamer.cpp
index 6ce7ae8..573308a 100644
--- a/lib/MC/MCPureStreamer.cpp
+++ b/lib/MC/MCPureStreamer.cpp
@@ -28,9 +28,9 @@
   virtual void EmitInstToData(const MCInst &Inst);
 
 public:
-  MCPureStreamer(MCContext &Context, MCAsmBackend &TAB,
-                 raw_ostream &OS, MCCodeEmitter *Emitter)
-    : MCObjectStreamer(Context, TAB, OS, Emitter) {}
+  MCPureStreamer(MCContext &Context, MCAsmBackend &TAB, raw_ostream &OS,
+                 MCCodeEmitter *Emitter)
+      : MCObjectStreamer(SK_PureStreamer, Context, TAB, OS, Emitter) {}
 
   /// @name MCStreamer Interface
   /// @{
@@ -100,6 +100,10 @@
   }
 
   /// @}
+
+  static bool classof(const MCStreamer *S) {
+    return S->getKind() == SK_PureStreamer;
+  }
 };
 
 } // end anonymous namespace.