Add test case for <rdar://problem/8177927> (which triggered an assertion failure in SemaChecking).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108159 91177308-0d34-0410-b5e6-96231b3b80d8

test/Sema/struct-decl.c

@@ -41,3 +41,8 @@ struct s0 {
 };
 
 struct s0 f0(void) {}
+
+// <rdar://problem/8177927> - This previously triggered an assertion failure.
+struct x0 {
+  unsigned int x1;
+};