argv-iter: Improve GCC 11 allocation-deallocation checking

[Bruno Haible]

2021-08-07  Bruno Haible  <br...@clisp.org>

        argv-iter: Improve GCC 11 allocation-deallocation checking.
        * lib/argv-iter.h (argv_iter_free): Move declaration up.
        (argv_iter_init_argv, argv_iter_init_stream): Declare that deallocation
        must happen through 'argv_iter_free'.

diff --git a/lib/argv-iter.h b/lib/argv-iter.h
*** a/lib/argv-iter.h
--- b/lib/argv-iter.h
***************
*** 30,42 ****
    AI_ERR_READ
  };
  
! struct argv_iterator *argv_iter_init_argv (char **argv)
    _GL_ARG_NONNULL ((1));
  struct argv_iterator *argv_iter_init_stream (FILE *fp)
!   _GL_ARG_NONNULL ((1));
  char *argv_iter (struct argv_iterator *, enum argv_iter_err *)
    _GL_ARG_NONNULL ((1, 2));
  size_t argv_iter_n_args (struct argv_iterator const *)
    _GL_ATTRIBUTE_PURE _GL_ARG_NONNULL ((1));
- void argv_iter_free (struct argv_iterator *)
-   _GL_ARG_NONNULL ((1));
--- 30,43 ----
    AI_ERR_READ
  };
  
! void argv_iter_free (struct argv_iterator *)
    _GL_ARG_NONNULL ((1));
+ 
+ struct argv_iterator *argv_iter_init_argv (char **argv)
+   _GL_ARG_NONNULL ((1)) _GL_ATTRIBUTE_DEALLOC (argv_iter_free, 1);
  struct argv_iterator *argv_iter_init_stream (FILE *fp)
!   _GL_ARG_NONNULL ((1)) _GL_ATTRIBUTE_DEALLOC (argv_iter_free, 1);
  char *argv_iter (struct argv_iterator *, enum argv_iter_err *)
    _GL_ARG_NONNULL ((1, 2));
  size_t argv_iter_n_args (struct argv_iterator const *)
    _GL_ATTRIBUTE_PURE _GL_ARG_NONNULL ((1));