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/WinCOFFStreamer.cpp b/lib/MC/WinCOFFStreamer.cpp
index b529489b..75f343c 100644
--- a/lib/MC/WinCOFFStreamer.cpp
+++ b/lib/MC/WinCOFFStreamer.cpp
@@ -75,6 +75,10 @@
   virtual void EmitWin64EHHandlerData();
   virtual void FinishImpl();
 
+  static bool classof(const MCStreamer *S) {
+    return S->getKind() == SK_WinCOFFStreamer;
+  }
+
 private:
   virtual void EmitInstToData(const MCInst &Inst) {
     MCDataFragment *DF = getOrCreateDataFragment();
@@ -128,13 +132,10 @@
 };
 } // end anonymous namespace.
 
-WinCOFFStreamer::WinCOFFStreamer(MCContext &Context,
-                                 MCAsmBackend &MAB,
-                                 MCCodeEmitter &CE,
-                                 raw_ostream &OS)
-    : MCObjectStreamer(Context, MAB, OS, &CE)
-    , CurSymbol(NULL) {
-}
+WinCOFFStreamer::WinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB,
+                                 MCCodeEmitter &CE, raw_ostream &OS)
+    : MCObjectStreamer(SK_WinCOFFStreamer, Context, MAB, OS, &CE),
+      CurSymbol(NULL) {}
 
 void WinCOFFStreamer::AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                       unsigned ByteAlignment, bool External) {