bug#40780: guile 3.0.2: Prevent warning using libguile with -Wpedantic (redefinition)

[Hannes Müller]

Dear Maintainer,

2 warnings as shown below for libguile 3.0.2 (i.e. usage of libguile in
external C code) with gcc 9.3.0 and option -Wpedantic are indicated. In
contrast I get no warnings for libguile 2.2.7 with the same compiler
options. Therefore, please fix this easy to circumvent warning. 

Best regards
Hannes

In file included from /usr/include/guile/3.0/libguile/numbers.h:29,
                 from /usr/include/guile/3.0/libguile/array-
handle.h:27,
                 from /usr/include/guile/3.0/libguile.h:35,
                 from read_cfg.c:7:
/usr/include/guile/3.0/libguile/print.h:79:3: warning: redefinition of
typedef 'scm_print_state' [-Wpedantic]
   79 | } scm_print_state;
      |   ^~~~~~~~~~~~~~~
In file included from /usr/include/guile/3.0/libguile.h:33,
                 from read_cfg.c:7:
/usr/include/guile/3.0/libguile/scm.h:824:32: note: previous
declaration of 'scm_print_state' was here
  824 | typedef struct scm_print_state scm_print_state;
      |                                ^~~~~~~~~~~~~~~


In file included from /usr/include/guile/3.0/libguile/threads.h:27,
                 from /usr/include/guile/3.0/libguile/async.h:25,
                 from /usr/include/guile/3.0/libguile.h:38,
                 from read_cfg.c:7:
/usr/include/guile/3.0/libguile/dynstack.h:37:3: warning: redefinition
of typedef 'scm_t_dynstack' [-Wpedantic]
   37 | } scm_t_dynstack;
      |   ^~~~~~~~~~~~~~
In file included from /usr/include/guile/3.0/libguile.h:33,
                 from read_cfg.c:7:
/usr/include/guile/3.0/libguile/scm.h:825:29: note: previous
declaration of 'scm_t_dynstack' was here
  825 | typedef struct scm_dynstack scm_t_dynstack;
      |                             ^~~~~~~~~~~~~~