[PATCH][gdb/symtab] Fix data race in cooked_index_functions::expand_symtabs_matching

[Tom Tromey]

>>>>> "Tom" == Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> writes:

Tom> +  void wait ()
Tom> +  {
Tom> +    for (auto &item : m_vector)
Tom> +      item->wait ();
Tom> +  }

This should have an introductory comment.

Tom