Produce a hidden symbol for zed in

  struct HIDDEN foo {
  };
  template <class P>
  struct bar {
  };
  template <>
  struct HIDDEN bar<foo> {
    DEFAULT static void zed();
  };
  void bar<foo>::zed() {
  }

Before we would produce a hidden symbol in

  struct HIDDEN foo {
  };
  template <class P>
  struct bar {
  };
  template <>
  struct bar<foo> {
    DEFAULT static void zed();
  };
  void bar<foo>::zed() {
  }

But adding HIDDEN to the specialization would cause us to produce a default
symbol.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@157206 91177308-0d34-0410-b5e6-96231b3b80d8