Fix some minor MSVC compiler warnings.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76356 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/Spiller.h b/lib/CodeGen/Spiller.h
index f339336..9c3900d 100644
--- a/lib/CodeGen/Spiller.h
+++ b/lib/CodeGen/Spiller.h
@@ -14,7 +14,7 @@
 
 namespace llvm {
 
-  struct LiveInterval;
+  class LiveInterval;
   class LiveIntervals;
   class LiveStacks;
   class MachineFunction;