Give MC/MCDisassembler/Disassembler.h a header guard.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130096 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCDisassembler/Disassembler.h b/lib/MC/MCDisassembler/Disassembler.h
index 6208b1c..f0ec42a 100644
--- a/lib/MC/MCDisassembler/Disassembler.h
+++ b/lib/MC/MCDisassembler/Disassembler.h
@@ -13,6 +13,10 @@
 // syntax.
 //
 //===----------------------------------------------------------------------===//
+
+#ifndef LLVM_MC_DISASSEMBLER_H
+#define LLVM_MC_DISASSEMBLER_H
+
 #include "llvm-c/Disassembler.h"
 #include <string>
 #include "llvm/ADT/OwningPtr.h"
@@ -88,3 +92,5 @@
 };
 
 } // namespace llvm
+
+#endif