maint: remove GLOBAL as per GCC 14

* src/common.h (GLOBAL): Remove this macro, and all its uses.
It collides with GCC 14 and -Wmissing-variable-declarations.
Change all uses of GLOBAL to use extern instead,
and declare the variables in their respective .c files.
Move .c file’s extern declarations here, so that they
appear only once and are checked against definitions.
* src/names.c (unconsumed_option_tail): Now static.

src/tar.c

@@ -30,12 +30,94 @@
 # define SIGCHLD SIGCLD
 #endif
 
-/* The following causes "common.h" to produce definitions of all the global
-   variables, rather than just "extern" declarations of them.  GNU tar does
-   depend on the system loader to preset all GLOBAL variables to neutral (or
-   zero) values; explicit initialization is usually not done.  */
-#define GLOBAL
 #include "common.h"
+/* Define variables declared in common.h that belong to tar.c.  */
+enum subcommand subcommand_option;
+enum archive_format archive_format;
+int blocking_factor;
+size_t record_size;
+bool absolute_names_option;
+bool utc_option;
+bool full_time_option;
+int after_date_option;
+enum atime_preserve atime_preserve_option;
+bool backup_option;
+enum backup_type backup_type;
+bool block_number_option;
+unsigned checkpoint_option;
+const char *use_compress_program_option;
+bool dereference_option;
+bool hard_dereference_option;
+struct exclude *excluded;
+char const *group_name_option;
+gid_t group_option;
+bool ignore_failed_read_option;
+bool ignore_zeros_option;
+bool incremental_option;
+const char *info_script_option;
+bool interactive_option;
+uintmax_t occurrence_option;
+enum old_files old_files_option;
+bool keep_directory_symlink_option;
+const char *listed_incremental_option;
+int incremental_level;
+bool check_device_option;
+struct mode_change *mode_option;
+mode_t initial_umask;
+bool multi_volume_option;
+struct timespec newer_mtime_option;
+enum set_mtime_option_mode set_mtime_option;
+struct timespec mtime_option;
+char *set_mtime_command;
+char *set_mtime_format;
+int recursion_option;
+bool numeric_owner_option;
+bool one_file_system_option;
+bool one_top_level_option;
+char *one_top_level_dir;
+char const *owner_name_option;
+uid_t owner_option;
+bool recursive_unlink_option;
+bool read_full_records_option;
+bool remove_files_option;
+const char *rsh_command_option;
+bool same_order_option;
+int same_owner_option;
+int same_permissions_option;
+int selinux_context_option;
+int acls_option;
+int xattrs_option;
+size_t strip_name_components;
+bool show_omitted_dirs_option;
+bool sparse_option;
+unsigned tar_sparse_major;
+unsigned tar_sparse_minor;
+enum hole_detection_method hole_detection;
+bool starting_file_option;
+tarlong tape_length_option;
+bool to_stdout_option;
+bool totals_option;
+bool touch_option;
+char *to_command_option;
+bool ignore_command_error_option;
+bool restrict_option;
+int verbose_option;
+bool verify_option;
+const char *volno_file_option;
+const char *volume_label_option;
+bool posixly_correct;
+const char **archive_name_array;
+size_t archive_names;
+const char **archive_name_cursor;
+char const *index_file_name;
+int open_read_flags;
+int open_searchdir_flags;
+int fstatat_flags;
+int seek_option;
+bool unquote_option;
+int savedir_sort_order;
+bool show_transformed_names_option;
+bool delay_directory_restore_option;
 
 #include <argmatch.h>
 #include <c-ctype.h>
@@ -92,8 +174,6 @@ request_stdin (const char *option)
   stdin_used_by = option;
 }
 
-extern int rpmatch (char const *response);
-
 /* Returns true if and only if the user typed an affirmative response.  */
 int
 confirm (const char *message_action, const char *message_name)
@@ -2174,7 +2254,6 @@ parse_opt (int key, char *arg, struct argp_state *state)
   return 0;
 }
 
-extern struct argp names_argp;
 static struct argp_child argp_children[] = {
   { &names_argp, 0, NULL, GRID_FILE_NAME },
   { NULL }