Add mising #ifdef guards.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@86002 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Analysis/PathSensitive/Checkers/UndefinedArgChecker.h

@@ -12,6 +12,9 @@
 //
 //===----------------------------------------------------------------------===//
 
+#ifndef LLVM_CLANG_UNDEFARGCHECKER
+#define LLVM_CLANG_UNDEFARGCHECKER
+
 #include "clang/Analysis/PathSensitive/CheckerVisitor.h"
 
 namespace clang {
@@ -28,3 +31,4 @@ public:
 };
 
 }
+#endif