Add a tricky, tricky test case for PCH that we currently don't handle. Committed with a FIXME so that we don't forget it

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@69052 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/PCH/struct.h b/test/PCH/struct.h
index e3d85ab..6c25622 100644
--- a/test/PCH/struct.h
+++ b/test/PCH/struct.h
@@ -23,3 +23,7 @@
 
 struct Fun2;
 struct Fun2 *fun2;
+
+struct S {
+  struct Nested { int x, y; } nest;
+};