Add the testcase from pr13168.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158950 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/pr13168.c

@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -emit-llvm %s -o -
+
+typedef int (*_MD_Open64)(int oflag, ...);
+_MD_Open64 _open64;
+void PR_OpenFile(int mode) {
+_open64(0, mode);
+}