[Parser] Handle #pragma pack/align inside C structs.

Fixes PR13580. Patch by Serge Pavlov!

llvm-svn: 179743
diff --git a/clang/test/Parser/pragma-pack.c b/clang/test/Parser/pragma-pack.c
index 84778cd..172a332 100644
--- a/clang/test/Parser/pragma-pack.c
+++ b/clang/test/Parser/pragma-pack.c
@@ -30,3 +30,17 @@
 
 _Pragma("pack(push)")
 /* expected-warning {{expected integer or identifier in '#pragma pack'}}*/ _Pragma("pack(push,)") 
+
+// PR13580
+struct S
+{
+  char a[3];
+#pragma pack(1)
+  struct T
+  {
+    char b;
+    int c;
+  } d;
+#pragma pack()
+  int e;
+};