Rename test.cc files to test.cpp.

The lit.cfg files only add .cpp to suffixes, so these tests used to never run,
oops.  (Also tweak to of these tests in minor ways to make the actually pass.)

llvm-svn: 224718
diff --git a/clang/test/CodeGen/builtin-recursive.cpp b/clang/test/CodeGen/builtin-recursive.cpp
new file mode 100644
index 0000000..67d8a44
--- /dev/null
+++ b/clang/test/CodeGen/builtin-recursive.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -nostdsysteminc -nobuiltininc -isystem %S/Inputs -emit-llvm-only %s
+
+// This used to cause a read past the end of a global variable.
+
+#include <stdio.h>
+
+void testcase(void) {
+  vprintf(0, 0);
+}
+