Pacify gcc -Wmissing-variable-declarations

This is a new warning diagnostic in GCC 14.
* lib-src/etags.c (mercury_heuristics_ratio):
* src/pgtkselect.c, src/xselect.c (selection_request_stack):
* src/xselect.c (outstanding_transfers):
* src/xterm.c (pending_selection_requests)
(x_dnd_waiting_for_motif_finish_display):
Now static.
* lib-src/make-docfile.c (close_emacs_globals):
Arrange for lispsym to be declared with extern first,
when compiling lread.c.
* src/alloc.c (gdb_make_enums_visible) [__GNUC__]:
* src/emacs.c (RCS_Id):
* src/keyboard.c (stop_character):
* src/print.c (print_output_debug_flag):
Now declared with extern first.
* src/lisp.h (DEFINE_GDB_SYMBOL_BEGIN) [MAIN_PROGRAM]:
Arrange for ID to be declared extern first.
* src/lisp.h (garbage_collection_inhibited):
* src/xterm.h (x_frame_parm_handlers):
Declare here, so that its interface is properly checked.  Other decls
removed.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 4226cb1d1a0..28e32554472 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -8338,7 +8338,7 @@ enum defined_HAVE_PGTK { defined_HAVE_PGTK = false };
    then xbacktrace could fail.  Similarly for the other enums and
    their values.  Some non-GCC compilers don't like these constructs.  */
 #ifdef __GNUC__
-union
+extern union enums_for_gdb
 {
   enum CHARTAB_SIZE_BITS CHARTAB_SIZE_BITS;
   enum char_table_specials char_table_specials;
@@ -8353,5 +8353,6 @@ union
   enum pvec_type pvec_type;
   enum defined_HAVE_X_WINDOWS defined_HAVE_X_WINDOWS;
   enum defined_HAVE_PGTK defined_HAVE_PGTK;
-} const EXTERNALLY_VISIBLE gdb_make_enums_visible = {0};
+} const gdb_make_enums_visible;
+union enums_for_gdb const EXTERNALLY_VISIBLE gdb_make_enums_visible = {0};
 #endif  /* __GNUC__ */