Add support for the new va_arg instruction

llvm-svn: 6029
diff --git a/llvm/lib/VMCore/Instruction.cpp b/llvm/lib/VMCore/Instruction.cpp
index 01381fa..ce1423a 100644
--- a/llvm/lib/VMCore/Instruction.cpp
+++ b/llvm/lib/VMCore/Instruction.cpp
@@ -91,7 +91,8 @@
   case Call:    return "call";
   case Shl:     return "shl";
   case Shr:     return "shr";
-    
+  case VarArg:  return "va_arg";
+
   default: return "<Invalid operator> ";
   }